Carl Paoli has a quick 3 part L-Sit Progressions series. On Parallel Bars with tucked knees, keeping hips forward P-Bars L Sit Negatives Floor straddle L Sit drill
How to do a backflip – Tutorial
Carl Paoli teaches 2008 CrossFit Games Champion Jason Khalipa the backflip. A nice step by step break down into useful progressions.