Thanks for this link:
The wheel rim is a clever form for the oven opening. Much better than the angle iron for those who don't want to build a masonry arch.
Also, the oven building armature made of strips of flexible wood held up by the soldier course is very clever. You can get in the oven to fix joints, and you can burn out the form once the oven cures.
I'm not happy to see another "how to build an oven" link with the cooking floor sitting on tons of rock and sand. At least they call it a "heat sink". Isn't it just.