depending on the size, cut a flap into a drink bottle lid. ready made hide that's easy to clean and no chance of mould etc like paper. Even large plastic/fabric leaves they can crawl under is all they need too.Cheers.
I put an egg carton "hide" in there but he seems to like being visible.
Am enjoying my slings, and expect a c. versi sling any time today (from spider world, poland)