Starting in a shark from right to left, push both hands forwards to flatten the kite out (as per the switchback), but before the kite flattens out totally, pop with the right hand to execute a 540 flat spin off the ground. Looking down from above, the kite Flat Spins anti-clockwise. Pop again to get Leading Edge 900's, 1260's etc., etc.
A totally, totally excellent combination move is to start with a very low 540 flat spin at one edge of the window, come directly out into a shark, drag all the way across the window, switchback, shark all the way back to where you started and then pop a leading edge 540 flat spin back into flight.