A dual-purpose urn-shaped clay oven is traditionally configured for baking flatbread on the inner sidewalls thereof. To increase its utility in a commercial bakery, a removable tray system is provided allowing using the oven for baking conventional bread products. The tray system includes a number of frame segments extending radially from a common vertical axis and rotatably supported below the oven cover. The oven cover has a door to partially access the oven and allow rising of one frame segment at a time from the oven to replace the bread products with unbaked dough. Each frame segment supports a number of vertically stacked baking trays configured for holding bread while baking. Also described is a conversion kit to adapt an existing oven for dual-purpose use.