Yep, I second the lining of that box in some way. Personally, I think a good option would be Formica, or maybe vinyl floor covering. You can get it in about any color at hardware stores. You cut it to one piece per side/bottom/top, and only need to worry about sealing where the walls meet the bottom and top. Use a silicone sealant for that. that should keep it from getting to your wood, and would be easy to clean up.