1) Lay on your left side with your left arm on the floor in front of you and your right arm on your side.
2) Now move your legs as if your walking backwards and push off with your left leg pushing the lower part of your body backward. At the same time move your arms in a similar manner but push off with your left arm pushing the upper part of your body backwards.

If done correctly you will smoothly flow backwards while looking as if your not supposed to move at all.