Wood humidor construction questions

[kingcobradude]

I have been planning on building a wood humidor out of some lovely walnut I have in my shop, but noticed in a lot of humidor building videos/guides, they use plywood for the top and bottom. Do I need to use plywood there, or can I use walnut there as well? I presume that I need to seal the walnut on the inside anyway before adding the Spanish cedar, right?