Starting Position: Lie prone (on your stomach) over the top of a properly-inflated stability ball (one that compresses approximately 6″ under your body weight) with both feet and hands on the floor, hip- and shoulder-width apart.
Gently exhale, contract your abdominal/core muscles to stiffen your torso and slowly walk yourself forward, lifting your legs off the floor. Continue walking out until your toes, with ankles in dorsiflexion (toes pointed towards your shins), rest on the top of the ball. Maintain a rigid torso aligned parallel with your legs. Retract and depress your scapulae (pull your shoulder back and down) as your reach your end position, with your arms fully extended and hands positioned directly under your shoulders.
Curling Phase: Exhale and while keeping your legs fully extended, pull your feet towards towards your chest, rolling the ball forward as your hips move upwards (think about lifting your rear end towards the ceiling while hinging at the hips). Continue moving until you reach an inverted position where your hips are positioned directly above your shoulders, with your legs, torso and arms fully extended, and head positioned between your arms. Your toes should remain on the top of the ball, but your ankles can move into plantar flexion (toes pointed away from your shins).
Lowering Phase: Inhale and slowly lower yourself back towards the floor, returning your body to the starting position.