Here is a quick list:
1) You need to get some way to control the UTH. A thermostat will work best, but you can also use a rheostat or a lamp dimmer. You can get those at hardware or home improvement stores.
2) Cover the UTH with something. If plexiglass is not an option, you can try getting a cheap plastic tub and cutting the bottom out of it and mounting it with some small wood screws to hold it down over the UTH. Just something to protect it from the snake, urine, feces,or spilled water.
3) Two identical hides. One over the UTH and one on the other side.
4) Water bowl. This doesn't really need to be big enough for the snake to soak in, but a larger shallow bowl will help with the humidity.
5) Digital temperature/ humidity gages will give you more accurate readings than the dial or tape stick on type...
6) If the heat lamp is mounted inside the enclosure, you need to make sure there is a screen around it so your snake cannot touch the bulb...