Leave the platform and turn around at the front end. Swing back to the platform and then back towards the frontend. On your way back, sweep back hard and rise into a Seven position with the hips pushed towards the bar and your legs open. At the peak of the swing, let go of the bar and start the turn, closing your legs at the same time to accelerate the spin and make two and a half turns before making the catch.
You can find out more about this trick in my books: