Ok here are some simple step by step instructions on how to make one with pics.
First step is to get a container that will be an appropriate size for your T to fit in, don't want them to be all scrunched up in there, but also don't wanna give them too much extra room.
Second step is to drill holes in the lid and sides for ventilation.
Here in this pic I've gotten the container and drilled holes....
Then take a paper towel, or coffee filter and place it inside the deli cup. Make sure it doesn't cover the holes in the side, which I didn't do in this pic because I was doing it quick, but you get the idea.
Then spray the entire paper towel/coffee filter down with water.
Next add your tarantula to the deli cup...
Then, and this is important, put the lid on..
Then put it some place warm, quiet, and dark. Leave the T alone and check on it in a couple hours. Personally I put them in a paper bad next to my heater in my room, which is always quiet since I'm hardly ever in there lol.
And that's it, it's that simple.
Special thanks goes out to my immature male new river for his assistance in this demo. Please note, there is nothing wrong with him, aside from having lost a spinneret awhile back before I owned him, and he's since molted because it's already started to come back, Should be fully back with his molt, which during the photo shoot I noticed could be sooner rather then later.