Lay on the floor with a neutral pelvis, hands at your sides, and your feet together on the chair. If you don't have a rolling chair, rest your heels on a small towel (if you're on a smooth floor) or on two sliders or paper plates (if you're on carpet).
Pull in your abdominal muscles and engage your glutes to press your hips toward the ceiling.
Take a breath in, then push the chair away on an exhale, keeping the sides of your waist even.
Inhale to bring the chair back in to the starting position. This counts as one rep.