This move originated in Capoeira (Brazilian Martial Arts) in which it is known as Au Batido (`ow bachito).
It's really not easy but when mastered you're a damn good breaker.
1) Stand with your hand above your head.
2) Swing it down to the ground (at that time do a one handed hand stand).
3) Bring your legs up to a 90 degree angle.
4) Stay up in that position for a few seconds (if you look at your legs sideways they look like an L).
Keep practicing the L-Kick or you'll hurt yourself if you haven't practiced.