Swing out. At the frontend, bring your legs up in front of you and pass them in between your hands as if you were going to hook your knees on the bar. Instead, hold the bar higher up your thighs. At the backend, push your body straight so the bar moves higher up your thighs (just under your butt). Your arms should be straight. Squeeze your butt! At the peak of the swing, let go of the bar and drop to the catch.

These notes are provided ONLY as an explanation of the trick.
If you want to perform it yourself - get an expert to teach you.
Other variants of this trick: