I have a spare heating mat from a waterbed. I was going to use it in a huge setup, but during tryout, I ran into problems.
For one thing, when I set the temp for ninety, I stood on it to see how hot it got.......it got super hot for about 3 minutes and turned itself off. They are designed to heat a whole bladder of water to a certain temp, and to do that they turn on emmiting mega heat to heat up the whole bladder. It doesn't stay on at a set temp. So when I tried it without the bladder, it would realize temp was not right, come on hardcore for a couple minutes, realize it was too hot, and shut off until the mat cooled below ninety and start all over again.
Of course most of them read right on the mat "do not use unless under FULL water matress", but I had to try out what could have been a kickass heat pad. Too bad it didn't just radiate 90 degrees 24/7 instead of turning itself off and on all the time, but apparently that's how they work. I wound up getting a heating pad and not risking burning my bp or possible the house.
So, put it on the floor, set the temp and plug it in. Then either stand on it in your socks, or press your arms and hands against it all over searching for hot spots. Yours may be different than the ones I've seen, but if it's going into a larger cage you could maybe use it under your big water source to keep it at desired temps if you find places that get hot enough to roast your snake.