Flyer 1 swings out and gets up into a sitting position on the bar. Flyer 2 jumps onto the bar from the platform and swings underneath. At the frontend, the Flyer 2 lifts their legs up (together) and places their feet in between the thighs of Flyer 1, who squeezes their thighs shut. They swing back to the platform. Flyer 2 releases their hands and hangs down from their feet. At the frontend, Flyer 2 gives their hands to make the catch.
This trick can be more easily performed on a bar-to-bar rig where the timing of the catch is less important.
Note that when Flyer 2 lifts their legs up at the frontend, they have the option to release their hands and hang from their feet at the back (this trick - analogous to a Knee Hang catch in terms of timing) or to hold on and release at the frontend (first hands, then feet - analogous to a Hocks Off timing). There is a video below of each option.
Either flyer can wear safety lines (Regular Lines) for this trick, but not both. It makes most sense for Flyer 2 to wears the lines as they are the one making the catch.