This is an unusual trick, based on the Bird's Nest.
Swing out with your hands slightly further apart than usual. At the frontend, bring your legs up in front and place the top of one foot (shoe laces) on the bar, next to the hand on the same side. Pass the other leg through your hands and straighten it under the bar. Keep your butt in between your arms so you are balanced. At the back end, push your butt forward so that it passes between your hands and push your head back so your back arches. The final position is very similar to a Bird's Nest, but with one leg free (which makes it harder and less stable). Just before the peak, unhook your foot from the bar and give both legs to the catcher then let go.
You can find out more about this trick in my books:
Thanks to the team at Circus Arts Australia for providing this video.