I'm working on a collar for my chest freezer. I was planning on staining the wood and adding a layer of insulating foam I have - was wondering if I should wrap the inside of the wood with plastic sheeting. Any thoughts?
I used plastic 2x6 fencing material; no rot issues, and it's hollow inside, so I was able to fill it with extruded polystyrene insulation as well as use it as a conduit for running my wiring to the Love controller.
The way to go is a good urethane varnish, inside and out. Make certain it is compatible with the stain and let the stain dry 3-4 times as long as the directions say.
It may be too late now, as it sounds like you've purchased your materials already, but I would recommend you use pressure treated wood. It won't warp and it won't require the use of insulation. The stuff's great for this sort of application.