Sac is a large metal or ceramic lid like a shallow bell with which
bread dough or meat to be baked are covered, and over which ashes and live coals are placed. It enables even,
convection baking, and the bell shape allows the
steam to recirculate, which makes the
meat,
fish and
vegetables to remain juicy, and the
potatoes, and vegetables to intermix their flavors with that of the meat. It is also used for baking
bread and traditional
pastry like
burek and
pizza. The bell itself likely comes from bell-shaped ovens used for
flatbread baking in middle-east.