Mentioned earth ovens in a post and remembered this exists. Unfortunately the guy is very into...history. But the instructions are very clear and complete, and most importantly there are no animal products in this video.

How to cook with it (CW: Brief shot of salt pork in the intro)

Process of building a big oven for the post-apocalypse commune. Don't want to be caught unprepared when the rich hoard municipal methane supplies. (CW: Ambience includes a roast for some reason, unrelated to construction)