I prefer to just use plastic. You can take a plastic bin of the right size and make a few cuts and be done. Fill with spag moss and make it a humid hide. You can also just use a plastic planter cut in half to form 2 equal sized hides.
What kind of tort are you making the hide for?
When I'm making one, I try to keep these things in mind:
* dark (like a natural cave or burrow or hiding spot under a clump of bushes or roots)
* cozy and secure (should feel like a natural burrow - just big enough to crawl in and turn around)
* Substrate (holds moisture and provides something to dig in. Some torts like to cover themselves in moss and\or dirt to sleep)
I also like to provide a hide on the warm end (hot and humid) and one on the cool end (dry and 'cool') - but equal in size.
I have a pot that I use, but wanted to add another house. What I have on hand right now are all a tad too small, which is why I thought about connecting two to make one hide.
Hot glue is fine. So is aquarium silicone, after it cures for 24-48 hours. I'm with Chad though. I just go buy (or dig out of storage, usually) the appropriate sized "shoe box". I cut a door hole with a dremel tool, fill it with coco coir, dump in a bunch of water and call it done. Oh yeah, I usually partially bury them so there is no step up or down to get into them. Coco coir works great for me as it never molds or gets "yucky" in any way. Sometimes I'll throw in some long fibered sphagnum moss too.
In my baby Cherry-head Red-foot habitat, I am experimenting with a 'hide' made of brown paper bag torn up into rough shapes, layered about 3-4 deep, and dampened. There is almost always one under it, often 3, and occasionally all 4.
The goal here was to simulate the sorts of hides that torts have to squirm into and where slightly damp materials press their shells.
So far, I am happy with the results, although it takes more misting than I would have thought. I am going to try a simple drip system this weekend.