Fire Hazard Alert

It's my understanding that when wood gets hot repeatedly, it degrades more and more, making it easier to ignite. Everything can be fine for awhile, but then...
I believe that it's very risky to have plywood under the oven particularly if the plywood is sitting on a flat surface where air can't circulate.
However, if your floor mass is really substantial, I think a wooden base may be a little more protected from damaging heat, but I'm not certain about this.
If it's a tiny demonstration oven, then it might not matter because it would be difficult to bring a tiny oven up to a high operating temperature, but even here, there might be exceptions.
Based on what I've observed, I believe it's best not to have wood under the oven. Period.

 

Here is a photo of a demonstration portable brick oven where the brick floor sits directly on 3.5" of perlite. Supporting the oven is 3/4"plywood. The oven was assembled on a wooden picnic table, and the heat from the oven damaged the table. For safety purposes, the oven should have been assembled on saw horses and probably twice as much perlite should have been used.

More Flat Breads

Every time I make flat breads with my non-oven, I am continually amazed concerning how easy they are to make and how great they taste. Yes, I still bake loaves in my wood-fired oven, but the process is very complex indeed.
It's really difficult to achieve a flat bread failure and perhaps that's one of the reasons why flat breads are much more universally found than leavened loaves. Most flat breads do have some sort of leavening agent, and  yes, I know it's an oxymoron.
Just last night we made flat breads, added goat cheese, tomatoes, onions, garlic and extra virgin olive oil. We simply folded up the warm flat breads with everything inside (next time I'll try to include a photo), and I really can't recall anything ever tasting better.