Lie on your side with your arms and your legs extended. Bring your feet slightly in front of you so that you're in a hollow position. You can put one hand down for support if you need (as seen here).
While keeping your navel pulled into your spine, simultaneously lift your arm(s) and legs a few inches toward the ceiling.
Lower back down to the floor with control. This completes one rep. Do the same amount of reps on each side.