You can make one like others have done, but honestly, being new to this there are things you would never think of that experts have researched for years and years in building safe enclosures that clean easy and are user freindly. Id suggest AP (Animal Plastics) enclosures. 4 feet is fine thats what I use, but a hight and Depth of 3 feet is way to much for all kinds of reasons including heating easily, cleaning easy and snake feeling secure ect... You want a T10 $199! Thats 4'x24"x15". I'll post some things a lot of us use and you look at them if you want.
1) AP enclosures: http://www.apcages.com/home/
2a) Thermistat: cheap one that works good - Jump Start by Hydro farm. https://www.amazon.com/Hydrofarm-MTPRTC-Digital-Thermostat-Heat/dp/B000NZZG3S
2b) Best out there:Herpstat thermistats: http://www.spyderrobotics.com/index....products_id=24
3) Pro Panel Rhp heating: http://pro-products.com/pro-heat/
4) Reptile Basics hides: http://www.reptilebasics.com/hide-boxes
5) Acurite thermometer: https://m.lowes.com/pd/AcuRite-Digit...meter/50425266