Just a quick update for you guys who gave me advice. I put more rock in the bench and had to knock the feed tube down one brick. The feed tube was too tall and it was creating draft issues. I took the top layer of bricks off and now it rockets right away even on a cold start. No drafting issues... no back drafts. The hound slept right on the top.
Im almost done with it. Just have to dry the cob out a bit, get some metal tape for the seams, patch up the spots at the top of the feed tube, and clean the rocks and slate a bit more.
Linseed oil after it dries???