In my ongoing quest to reproduce the flat bread unearthed in grave finds at Birka and other locations, this weekend I got to try baking them in an earthen oven. I'll post pictures soon, but until then, a brief summary.
The oven was constructed by some friends of mine last fall. It's made from adobe, and is a dome shape about 4 feet in diameter and 2.5 - 3 feet high, with a smoke hole at the top, and an opening in the side just big enough to admit a metal baker's peel.
We fired the oven for probably 2-3 hours before any bread went in. For the first loaves, which were more modern sourdough loaves, we left some of the coals at the back of the oven, and put the bread in at the front. This left the oven way too hot, and the loaves blackened pretty seriously before they were done all the way through. For my flatbread, I scraped out the rest of the coals, and relied on the heat of the oven walls.
I used several different recipes, but the one that worked best was 1/2 whole grain barley flour, 1/4 oat flour, and 1/4 green pea flour, plus about 1/2 tsp of salt. I made a stiff dough using buttermilk, and left the dough unrefrigerated overnight to sour (it didn't, much). The dough was shaped into two flat "loaves", each about 8" in diameter, and 1" high. The surface was pricked with a knife before baking, to increase the surface area of the top crust and encourage drying.
The loaves went into the oven, and backed for probably around 20 minutes. As the oven cooled a bit, subsequent batches took slightly longer to firm up.
The result was quite good, with a crisp crust, and a nice texture. Not light, more like a heavy scone or batter bread in consistency. It went excellently well with some simple soft cheese and dried fruit.
I'll have some pictures up, hopefully this evening. I got pictures of the whole process.