I don't think that AACCA has any rules about stunting with signs. I know they have specific rules about throwing signs, and tumbling over signs,but I think same rules apply when stunting with or without signs. Maybe you see something different www.aacca.com
There was one I learned at a camp. It's like the group starts with like one base holding the flyers leg out, like in a straddle, and the other is on the ground. The flyer then jumps off the groups (assisted by the backspot) and the main base with the straddle-leg scoops it underneath which gives her height, and both feet are grabbed and pulled into a elevator or extension
My team does a sort of modified toss to hands when we use signs. Each base wraps their hands around a thigh and the back gets the waist. From there, just dip, toss, and bases catch feet and back catches ankles. It's really simple and easy.