i understand how to set yourself up, but not how to execute the movement.
it says » Roll as far as you can to your left (shuffle your feet) without changing your arm position or letting your hips drop.
in the two pictures, i dont see much difference in the guys movement, except that hes barely tilted to the left a little and i dont see much movement in his feet, but the directoins say to shuffle your feet.
That's a) because the exercise is WAY harder than it looks and you'll be surprised how far you CAN'T go and b) because the model sucked.
Move your feet as far as you can, keeping your torso in line with your hips (ie no leaning to one side) and your arms parallel to the floor (we use a dowel rod to monitor that). You begin by shuffling your feet to one side and can progress to stepping and then jumping on to one foot.
Ideally - you should end up with only your hand/forearm/upper arm on the ball.