Skating Backwards is more difficult and different to skating forward as it has a different motion compared to skating forward.
From the normal hockey position, with whichever leg you start off with, you push off as if one of your feet were in the snow plow position. As you could the players feet is slightly faced towards the middle, he pushed off to get power. However, without raising your feet you keep the foot that pushed off on the ice bringing it back to your original position, also known as the C-Cut. You would then use your opposite leg creating a patter back and forth.