I've never used powerbait before so I am only assuming that you wad it up like a small ball and put it on the hook shank. That said, if you decide to "tie" these flies, the easiest way to do it would be to use a Dremel like a miniature lathe, with a VERY heavy duty carpet needle as a spindle. With it set to one of the slower speeds, impale an appropriate sized chuck of flip-flop foam on the needle and use an Emory board to shape flip-flop foam to a ball. When it's shaped the way you want it, push the eye of the hook through the hole made in the foam ball. Before you insert the hook, put a base of thread on the hook shank. Add a drop of super glue when you slide it on and it will stay in place. If you look up an article here by Jim Hatch called Dreml bugs you'll see how to use the Dremel.

Jim Smith