I suppose you can stain it and put a liner. I’ve seen some put linoleum down for liner. We bought a 4x8 Dairy Barn Panel at Home Depot for $25. It’s white, one side is smooth. We cut the edges to fit inside the coop so it would preserve the flooring and for easier clean ups.
We just bought our first chicken coop 4x8. We bought the materials for the chicken run inspired by your posts. We will be getting our laying hens on Monday, 8 Red Stars and 4 Black Stars. We are all excited!