Welcome to the site. I'm still new at this too, but if I could make a suggestion. I've read plenty of posts saying that cardboard can be bad for mold growth after awhile. I've had luck finding containers to make hides from the dollar store. Currently I am using two tortilla warmers turned upside down with a hole cut out on the bottom of the container. My guy seems to like them a lot.
Good luck and once again, welcome.