I used a relatively thin scrap leather. Use the Set focus feature if you’re not sure. It’s a tight fit, so if you’re using thicker leather you may have to tweak the file and make the pattern wider.
I used 6mm rivets for the sides and an 8mm rivet at the top.
I’ve got patterns for sewn versions, but I really like the rivets. I’ve seen a lot of sewn hand sanitizer holders, though, so I was thinking of seeing if I could make one with a similar vibe to yours! But maybe with cork…