Make it sturdy and design in escape proof as a guiding principle - these are strong, strong snakes.
Think about how to heat, light and clean it before you start designing.
What size of burm is it for? Is it easy to handle, hook trained etc - i.e. do you need the opening to be in the front to get him out and able to open fully to avoid having to lift a heavy snake who may not want you to be lifting him.
Would having the front hinge down to form a ramp down to the floor be a good idea - or would you just end up with a carpet full of snake pee? Perhaps some form of rounded lip could be used to avoid that.
That should keep you going till the people who know what they are talking about arrive.
dr del
Derek
7 adult Royals (2.5), 1.0 COS Pastel, 1.0 Enchi, 1.1 Lesser platty Royal python, 1.1 Black pastel Royal python, 0.1 Blue eyed leucistic ( Super lesser), 0.1 Piebald Royal python, 1.0 Sinaloan milk snake 1.0 crested gecko and 1 bad case of ETS. no wife, no surprise.
You can waterproof a piece of furniture. We did. The grout is sealing all the extra holes and once we seal it it'll be great but also you can use a pond liner. I've seen both done.