Lie on your back and bend your knees, put your feet flat on the ground. Bend your elbows to 90 degrees. Bridge up, driving through your heels and upper back.
Drive your hips up as high as possible, squeezing your glutes hard as you brace your abs. Keep your belly button drawn in.
Squeeze your glutes for two seconds at the top and lower all the way back down to the ground before repeating. Do not rush through the move.