Mudfire IV - Dome disc

Mitch and Dustin brought over a disc from their farm implement junk pile.  When in place, the bottom of the disc will be directly above the reactor core, a 4- to 6-inch gap between the core and the disc. Above the disc will be an ordinary pizza stone, serving as the floor of the oven. Between the pizza stone and the disc will be... well, I don't know what. Yet. Maybe just hot air.
Plenty of time to ponder the disc-pizza-stone sandwich as the bottom of the bell gets thoroughly mudded.  It's going to take a few days to get the bottom ring prepared for the rest of the bell. Formwork for the upper bell will be built with a baker's dozen elm trees, each tree being four years old, plus or minus two years.
I used to think the etymology of the phrase "cobbled together" had something to do with shoes. Andersen and the brothers Grimm called the shoe maker a cobbler, didn't they? Now I know first hand how misleading those fairy tales were. Building a cob rocket stove is a daily illustration of cobbling something together that might just work - if it doesn't fall apart of its own weight first!