Start with a shorter bench then work up to a bench that allows your leg to be at a 90 degree angle when your foot is placed on it.

Start by standing with the bench in front of you. With control place a foot on the bench and step up, keeping the stepping knee stable and not moving in or out. When at a full stand on the one leg, the opposite knee will be bent and come through in front of you, with foot flexed. Sharply tap the opposite foot to the bench and bounce it immediately back off and into a dorsi flexed hip flexion. With control, step back down to ground.