Just a small correction in terms of modern flatbreads. Although the vast majority of modern flatbreads are made on a flat surface, the baking surface of the tandoor is actually concave - which means that the outer side is cooked on the stored heat of the tandoor walls while the inside is exposed to the slightly more intense heat coming from the fire so that the cooking speeds are balanced. But India also has its “handkerchief bread” tradition where a very thin bed is cooked on a convex surface with either a ceramic or metal bowl being inverted and heated from below over charcoal. 

Although most kadais - the traditional Indian cooking bowl - are metal nowadays I have seen ceramic ones at roadside stalls in both Himalchaya Pradesh and Mewar and in Mewar, which is the only area where I’ve actually watched a local making handkerchief bread, some of  the kadais have an incised base - although the one I saw was smooth

kathryn