It is good to master this trick on the trampoline.Try rondat-roundoff with palms on the ground at first.
The beginning is the same as frontflip. At the moment you can not see the ground underneath, the rotation comes. Legs are straight and tight. Your heels write a circle. Imagine that you are jumping in a slit between two walls. Legs and head form a line perpendicular to the ground.
Frequent mistakes:
Your arms are not over your head but forward. Rotation comes too early, weak bounce.