Establish an arch.

Plant your feet so that your knees are below your hips and your lower body is stable. Use your legs to push your butt closer to your shoulders. This should tilt your rib cage to put even more pressure into your traps - preventing them from sliding. This will protect your shoulders and pecs, while involving more muscle and weight.
Plant your feet
SET YOUR FEET
SET YOUR FEET
You don't want your heel to go [up and down] during the rep. If it's flat on the floor, it stays flat on the floor. It doesn't shuffle around and certainly doesn't move. That is gonna help your bench press tremendously because to keep your feet flat, you're gonna have to apply force... which is going to tighten the rest of the body up.
Elite FTS
FOOT PLACEMENT
FOOT PLACEMENT
The other option besides having the feet tucked back behind (with the knee lower than the hip) is gonna be to have the feet out wide and usually out in front of the athlete. This is gonna be very common for bigger lifters, lifters maybe with a longer shin who aren't able to get that tucked back position, or if you just don't have the mobility in the quads and hips... we're still trying to achieve knee below the level of the hip.
Juggernaut
What we want to create is pressure into the ground through both feet. Generally, I'd say a wider foot position is better, as that's going to lend itself to a bit more stability... Athletes who have their feet tucked back more aren't gonna get as much leg drive generally... We should be able to see her knee below the level of her hip. This is gonna help maximize tension throughout the leg. It's also gonna help ensure that her butt does not come off the bench.... trying to get as much foot down as possible is going to generally be better.
Juggernaut
Your knees should probably be out past your toes... Because you're arched, your hips should be higher than your knees... You want to be pushing your knees outward... so your glutes are activated and your legs are stable. In a good set up, someone should be able to come from the side and push on any portion of your body, whether your legs, your torso or your arms - ANYTHING and they should not move.
Neversate
After setting yourself up on the bench with your eyes in front of the barbell shoulders on the bench and your butt on the bench, you can move your feet as far back as possible while keeping them flat on the floor. Provided this is relatively comfortable, this can be your leg position for the bench.
Barbell Medicine
If you are looking at the lifter from the side, aligning the knee below the hip on the horizontal plane is important to create tension through the legs and putting you in a position to maximize use of your legs throughout the lift. Lifters with longer legs may need to put their feet wide and in front of them to achieve this position. Shorter legged lifters and those with great flexibility in their legs and hips may be able to tuck their feet back more to achieve this position.
...the way I like to bench is with my feet tucked back and on my toes. I used to bench with my feet wide and with my heels down. However, with this way, I feel tighter, and it’s impossible for my butt to come off the bench. Although I’m on my toes, I still drive my heels down hard for leg drive.
Pull your feet back a bit and place them as far out to the side as your hips will allow. Your feet should wind up somewhere between your knees and your hips. This is the most common foot position because it still allows for a good arch, it’s easier to keep your whole foot on the ground in this position, and it’s easier to get leg drive with this foot position than with your feet pulled way back under your body.
Stronger By Science
Foot position is arguably the most important factor for both leg drive and keeping your butt on the bench. When observing truly great benchers, you'll notice they often take one of two foot-positions: Toes down/heels up with legs tucked tightly to the bench, or Heels flat with feet out wide. Either foot position works to prevent butt-lifting while maintaining a firm setup and powerful leg drive, but choosing which one works best for you depends on a few factors. Shorter lifters will have more success with heels up and legs tucked, while taller lifters do best with heels flat and feet out. This is simply because lifters come in all shapes and sizes while competition benches don't. Nearly all benches are 18 inches high, but if your femurs are 20 inches long, good luck getting your feet tucked behind you without shredding a hip flexor!
The first thing that we're gonna do is we're gonna set up our foot position so that we can get into the proper [arch]. So I'm gonna have his feet further out so that his knee is below his hip. This is gonna allow us to drive back into the bench, similar to squatting. You're gonna make the same motion. So he is now going to squeeze his glutes and externally rotate his knees outward, which is coming from his glutes and his hips. This is going to produce the most amount of force, recruiting the most amount of muscle, giving the most amount of stability, which is going to move the most amount of weight.
Barbell Shrugged
The exact spot that you put your feet will vary based on your leg length, the height of the bench, your personal preference, etc... It is ok if your heel comes up off the ground... find out what works for you. Now that the balls of your feet are cemented into the ground, I want you to flex your glutes as hard as you can. This is not only going to help you keep your butt on the bench, but it's going to ensure that you have a stable set up. If someone bumped either side of your legs, your knees should not move at all.
Alan Thrall
Your hips can only flex as high as your knee is... so when you bring your knee down lower than the bench pad, your hip can't flex higher than the bench pad.
Push butt toward shoulders
USE THE RACK
USE THE RACK
Barbell Medicine
LEGS FIRST SETUP
LEGS FIRST SETUP
TWO WAYS TO ESTABLISH ARCH
TWO WAYS TO ESTABLISH ARCH
Alan Thrall
His hip is higher than his knee joint. That will allow him to get a lot of flexion... Now when he drives his legs back, it's actually gonna push him back onto his traps.
Juggernaut
I teach this by placing my arms behind the lifter when they set up. I tell them to use their legs to drive into my arms as hard as they can. Usually, this gets the point across!
HIPS WEIGH ZERO
HIPS WEIGH ZERO
Once your shoulders are set, hold them in place by bracing your hands against the uprights of the bench, and use your legs to push your hips back toward your shoulders. Make sure you’re actively pushing your chest up, and not just arching your lower back without driving your chest up as well, since getting your chest higher is why arching “works” in the first place.
Stronger By Science
Now, have your friend stand by your head and use their hands to block your shoulders. Their goal is to keep you from sliding upward off the bench. Now, using your legs with your feet flat against the ground, push into their hands. What you should feel is a squeezing and supporting of the arch in your back
Barbell Logic
If you are not flexible, a great way to do it is start off by putting your feet on the bench and then you can just push your hands against the [rack], tuck your shoulders down and retracted, put your feet on the bench, and then push up into your arch. So keep in mind [your lower back] is not arching, [your upper back] is arching... When we're arching, our body should not go upward. lf the stomach is upward, that means you're arching with the wrong spot. You want your chest to be going up and back.
Barbell Shrugged
Tilt rib cage + press into traps
BENCH PRESS ARCH
BENCH PRESS ARCH
We should have more of an even extension through that thoracic spine. Other cueing that we can use, is to... put my hand under or kind of between her scapulas... and say don't touch me. That tends to bias people a bit more into that extension as well. Again, we're not looking for a huge arch and we're not even looking for you to maximize your arch from a competitive standpoint. We just want a global arch to be formed so that you have better tension, better leg drive, and a better foundation to actually press from...
Kabuki Strength
You don't want to be arching your lower back. That is probably not going to help you for two reasons: first of all, you're losing all the power that you could be transferring from your feet to the bar, and second of all you could be putting your back in a compromised position. You want to be arching your upper back... putting your upper back in that position allows you to also put your shoulders in a better position.
Mind Pump
Glass and Armstrong (1997) examined the level of pectoral muscle activation between the decline press and incline press. They found that the decline press activated more lower pec fibers compared to the incline press, while the level of upper pec activation was similar between both lifts.
The inverse (decline) bench press is the most effective exercise for the pectoralis major as a whole.
He's going to drive himself up into the bench. You will feel your traps below you when this happens. He's gonna have an arch in his back I should be able to pass my hand through.
Barbell Shrugged
What we're looking for in an arch is a nice global curve from the upper back all the way to the tailbone... We're anchored at the glutes, we're anchored at the shoulders... So the only motion that's happening is from the upper arm and not from the shoulder blade flopping all over the place.
Juggernaut
Start by anchoring your upper back into the bench. As you constantly retract your shoulder blades, rotate your shoulders down and under while you pick your chest up. This action locks in the lats and creates a stable arch
Protect + Involve
BENEFITS OF ARCHING
BENEFITS OF ARCHING
Jeff Nippard
WHY YOU NEED TO ARCH
WHY YOU NEED TO ARCH
ROTATE YOUR CHEST
ROTATE YOUR CHEST
Reactive Training Systems
Touching the bar lower on your chest obviously shortens the range of motion, assuming you get a decent arch. Not only does this decrease the effort required to complete each rep with a given load, it also keeps you from having to go through extreme ranges of motion that will inherently be weaker.
Stronger By Science
When you arch your back in the bench press, you are both raising your chest and the touch point that marks the bottom of the movement, shortening the distance vertically. You are also pulling your shoulder horizontally closer to that touch point as well, shortening the amount of horizontal travel away from the shoulder joint that is necessary for the safe execution of the movement. The arch improves the efficiency of an inherently inefficient movement.
Barbell Logic
You'll hear or read on the Internet is that this can cause a back injury by performing the bench this way... there's minimal compression and vertical loading of the spine when you're lying down, so overextension isn't too big of a problem from a purely mechanical analysis... There's probably some non-zero risk of back pain with performing an arch but it's probably not a big deal.
Barbell Medicine
You need lateral stability from your legs when you bench press. Lifting your legs off the floor while you're lying on a bench makes zero sense, and only makes the movement dangerous.
A little arch will help decrease range of motion a bit more. This will generally help you lift more weight and, more importantly, it will make the lift a little bit safer for your shoulders since the bottom position is where your shoulders are the most vulnerable.
Stronger By Science
When you arch your back in the bench press, you are both raising your chest and the touch point that marks the bottom of the movement, shortening the distance vertically. You are also pulling your shoulder horizontally closer to that touch point as well, shortening the amount of horizontal travel away from the shoulder joint that is necessary for the safe execution of the movement. The arch improves the efficiency of an inherently inefficient movement.
Barbell Logic
You want to arch your back as much as you can...to avoid injuries to your pecs
Arched benching (especially with a retraction of the scapulae) allows a greater use of the lower fibers of the pectoralis major (chest) muscles. Not only is this pushing angle likely safer for the glenohumeral joint of the shoulder, it’s also conducive to the great use of the larger mass of lower fibers of the pectoralis, which creates a more forceful lift without sacrificing as much safety as a flat pressing position might.
Juggernaut