Welcome to the divorced snake club!!! Ain’t it grand !!!!
no need for anything between substrate. Just get a good substrate and keep it damp but not tooo wet and a water bowl.
Get that themrostat asap!!!
also do yourself a favor and get a ceramic heat device to heat. Ditch the bulbs. I’ve been using one for a month and it stinks I’m going to full pvc and radiant heat soon.
Hang the CHE On the warm side w the UTH or to the middle then there will be a gradient hot hide middle and cool. Also make sure you have hides on at least each side or more if it’s a big tank