Last night I built a box for a couple of corn snakes I will be getting soon. I built it out of 1/2" plywood and used 3" flexwatt with a dimmer switch spliced into the power cord. It isn't quite finished yet, but I think you get the idea.
Click on the thumbnails for larger images.
This is the front:
http://i115.photobucket.com/albums/n...h_100_0252.jpg
This is the back:
http://i115.photobucket.com/albums/n...h_100_0255.jpg
Flexwatt inside:
http://i115.photobucket.com/albums/n...h_100_0254.jpg
Wiring of the dimmer
http://i115.photobucket.com/albums/n...h_100_0253.jpg