I make mine on the end of a mandrel but completely cover the end of it. (think vessel) I build up the bulk with clear (saves $$) and then I encase the clear with whatever base color I want. Then I decorate as wanted. I make sure that the bottom of the bead (facing the mandrel) is straight and even.
When I am done I anneal, clean it out and then I can cut the little mandrel thingy on the winestopper down to whatever size I need and epoxy it on.
I just found it too difficult to make sure that the bead I made was exactly the right size when using the top bead with the winestopper.