I keep them on sani chips or aspen with paper on top. The paper allows me to feed them without them ingesting bedding. I use blank news print which is sold for sandwich wrappers at kitchen supply stores. However, during the breeding season, I just use paper so that they don't get wood shavings in their cloacae, or hemipenes.
I have kept thousands of snakes on paper for 15 years without any issues. If you use newspaper, it's free, and easy to toss. I can also spray it down lightly to up the humidity for a brief period without oversaturating the cage. I just love the sani chips for hogs because they poop 12 times a day. lol.
The paper in these pics looks nasty because of the way I introduce my snakes. I place the male in the cage with the female, and leave them alone for 1-2 days. (if I see a lock, 1. If I don't see a lock, 2.) Then I remove the male, and feed both of them. After a couple of days I put them back together. This gives them time to get ready to breed again, but it also coincides with the last stage of digestion.
In short, I put them together, and they poop some time over the next two days. I can't get in and clean for fear of disturbing a lock, etc.