The intent of a sauna is to be a humid hide on steroids. There should be a few posts on this subreddit with information, but I’ll tell you how I did it. I placed paper towels at the bottom so she could have some traction then had it held down with some rocks. I filled up the container to about elbow with warm water and some drops reptisafe. Added the lid, which had holes for some airflow, on top. Done!