Lay flat on the bench with your feet on the ground. Roll a barbell up to the crease of your hips.
Place one foot flat on the floor under your knee as you would a normal hip thrust. With the other foot just bracing your stability with the heel but not taking the weight.
Drive the main foot into the floor and squeeze your glutes while bridging your hips up.
Lower your hips back to the starting position and repeat for the desired number of repetitions.