This photograph, taken by Reaktion Books publisher Michael Leaman in Tiblisi, Georgia, very clearly shows that the top of the oven is angled so that breads stuck to its side will receive direct radiant heat from the embers or fire at the bottom of the oven. If you build a tandoor oven I would use this photograph as a model.
The tandoor oven is the most common oven from the Caucuses to Northern India. The are a couple ways to think of the tandoor oven. The tandoor can be thought of as both a chimney and an oven wall built around a fire. Bread is slapped onto the heated wall where it sticks and bakes from a combination of heat stored in the wall and from radiant heat rising from the embers on the oven floor. Thus, while bread is baked on the floor of the domed bread oven it is baked on the wall of the tandoor oven. Tandoor breads are thus always “flat” though though they are often leavened with yeast or a sourdough starter.
As with the domed bread oven there is an initial hot firing to charge the oven walls with heat. If one starts baking too soon the ovens walls with char the bottom of the bread. If the embers at the bottom of the oven are too hot the heat rising from them will burn the bread before it is cooked. Most of the videos I’ve seen of baking in the oven just show the baking of the bread but don’t show how the oven is actually managed. If, by chance, you live in a country with tandoor ovens, please consider making a video for YouTube that shows the firing of an oven and that explains how the oven is managed for baking.
I selected this video for the introduction to the tandoor oven because it is a long video, five minutes, and thus really offers a look at a fairly complete baking cycle. It also shows aspects of the tandoor oven that is always clear. For example, the oven is clearly divided into two parts, the lower part where the fire is built and the upper part where breads are baked. That part is whitewashed. It is so cleanly whitewashed. There is no smoke on the whitewash which thus either tells us something about how the fire is operated or suggests that it was just whitewashed before the filming began. It also looks as if the fire was of brushwood.
At one point in the movie one sees a woman approach the oven and pour water on the embers. Tandoor ovens tend to be curved slightly at the top and you see here the bread browns sooner when it is on the curve. Perhaps these breads were browning too quickly and that is why the water was poured on the embers. (If you have experience operating a tandoor oven please comment.) At the end, when one of the breads is removed one sees that the bottom of the bread is a little burnt. I would thus guess that this is a first batch of bread going into the oven and the walls are a tad too hot and the embers still glowing just a tad too strongly.