Well, the ones I got from www.lurelayouts.com do not need to be clamped, clipped, etc. I just cut a piece big enough to stretch over the back and halfway or so down the sides, pull it tight at the bottom, and, you have an almost exact shape of your lure. Just make sure you do this on an unpainted one and then transfer it to the bait you're working on. They work pretty well, IMO.
Good Luck.