Flyer faces the front, backspot on the secondary side, secondary base on the main base side, and main base starts in backspot position.
Flyer jumps in with right foot back and uses the back foot to stand up on. Main base grabs like normal full up grip. Secondary base will throw and catch the foot like normal; same with the backspot going for the ankle.
The key is for the group to all replace each other fluidly. You have to get around fast or else the stunt will get caught. The flyer needs to stand straight up, main base needs to get the heel, secondary base get the other foot, and backspot keep the ankle sturdy. Also, everyone needs to stay chest-to-chest. Think of doing a 1.5 up instead of two because the stunt should catch to the back then turn to the front in one continuous motion.
I'm not sure if this is easy to follow, but it was worth a try!
Oh, and to answer your question: the main base will always have contact with the foot. The secondary throws and follows the other foot, just like a normal full up. There isn't a release.
Oh, sorry, I must have read your post wrong. I thought you were asking if there was a release completely from all bases. Yes, there is a release, but the main remains in contact with the foot.
This skill can however be done with a full release. When I do them in group stunts week them like a normal full-up but we all release at the top and let the flyer finish the second twisting rotation on her own before catching her.
But that way is difficult if you don't have experienced bases and or top persons.