First, set up the belt with a mat to protect your hips and prevent bruises (use the length that fits you best since there is two options).
Chins tucked in – think like holding an orange with your chins. Always look forward. This is the scoop method. Brace your core like you are about to get punched in your belly and only release breath out when you are close to the bottom on your way back. Maintain core tight at all times. Place the end of your shoulder blades on the bench.
You also can choose to do the hinge method with your head and neck neutral position and moving your torso as a whole unit, at the top position you look up to the ceiling.
Push the belt though your heels but feet is on the floor for stabilization.
Scoop method you maintain your chins tucked and move only your sternum down by posterior pelvic tilting.
Maintain your shins in vertical position at the top to bias glutes. If you put your feet far away you will feel more your hamstring. If you put feet too close you will more your quads. Adjust your feet as needed.
Squeeze the glutes hard at the top.
If your bench is very high you can go as much as you maintain your body in place and reverse mid-air to prevent from your shoulder blades getting out of the place.
Don’t let knees cave in. Maintain Spine neutral, don’t hyperextend your back. Maintain ribs down. Make sure you lockout with a full hip extension at the top while pelvic floor and spine and is in neutral position.