My brother-in-law has done this. I unfortunately was not available the weekend he put his together. At some point I plan to make one myself (much, much smaller than his - in fact, he says that is the one thing he would change for certain). If I remember correctly the inner portion of his is 4" of homemade clay bricks (mud) and the outer four inches of homemade brick insulation is clay + straw (cob). He used brick oven bricks for the floor of the oven and did not use any other insulation beneath (I think most instructions suggest wine bottles encased in clay/mud). I’ve gone so far as to check out a book from the library (can’t remember the book - I’ll see if I can figure it out later)
and came across this website a couple of years ago: www.pinkbird.org/w/How_to_build_a_pizza_oven. Tons of info on dimensioning with respect to heating and keeping a fire burning. Also, they have a small section on cob materials. And looking through some other notes that I had made, I see this website: www.sheffield-pottery.com. I’m guessing this was for a source of clay.
It was quite the ‘party’ putting that together. I’ll see if he has an open google folder with pics from that weekend.
The pictures I attached are ones that I took long after …
If you decide to make one, I can certainly help with the beer and wine bottles (should you choose to use them as insulation for the base - or even if you don’t).