Ahh, I see. I don't think you need to have anything under your soaps since the shelf is plastic. If you do put paper or something down and since you are troubleshooting the rancidity problem you are having, I would make sure you change the paper before a new batch is set on the shelf. I don't find it necessary to put anything over my soaps because I have a dedicated soaping space and not a lot of dust happens in that room. The space is in the basement and almost all hard surfaces (no carpet, furniture, pets etc.) Since my shelves are coated metal, I put a piece of embroidery plastic canvas under the soaps and I don't need to turn them as air can reach all sides. I sometimes place the paper with my recipe printed out over my cut bars while they are curing to keep track of how long they have been on the shelf. After about 2-3 weeks I will plane and bevel. After 4-8 weeks I will move them into a cardboard box for longer term storage.