In standing position, slightly bend your knees and widen your stance.
Hinge at the hips and have a slight bend at the knees. As you squat down, keep your back flat and head neutral and look forward. On the way up, drive with the legs and jump forward from the bottom so you become airborne. As you descend brace for the impact by landing gently on the balls of your feet on the box. Jump backwards whilst still looking forward to the starting position. Repeat.