One of the major temples in the fantasy culture I'm developing is devoted to food preservation and preparation, so I needed to find out more about ancient ovens. It's a more complicated topic than I thought it would be, honestly.
Quick Facts
The oldest archaeological evidence of people using earth ovens for food preparation comes from about 30,000 years ago.
Ceramics from the Jomon period of ancient Japan were probably fired in open fires instead of in kilns, which I didn't even realize was possible.
One of the ways the Harappan civilization may have been more advanced than their contemporaries was in using standard-sized oven-baked bricks instead of the hand-shaped sun-dried Mesopotamian variety.
Pottery kilns led to the development of metallurgy, which in Old Europe was widely viewed as special, almost magical.
The effectiveness of various materials as oven stones is a hotly debated topic in archaeological circles.
Central Bakeries
An early farming village near the Dniester River (Bernashevka) had a bakery with a domed clay oven as its central building. It was the only domed clay oven in the settlement, which had about 50 people and was located on a terrace over the floodplain. This bakery had wattle-and-daub walls and a thatch roof, but its floor was smooth fired clay over timber beams. (Source)
Bed Stoves
As early as 7,200 years ago, neolithic people in China were making heated floor beds. Early on this manifested as building fires on top of stone beds and then clearing the ashes, but eventually it turned into hooking up an oven flue to run beside the bed. This article goes into a ton of detail about the evolution of heated floors and beds in Asia.
Pit Ovens
The Maya probably cooked in pit ovens more often than other Mesoamerican cultures. They were generally about 40cm wide, 40cm deep, and a 1m long. The bottom was lined with limestone and covered with firewood. The wood burns until it heats the stone, then coals and unburnt wood is removed, and food wrapped in leaves placed on the stones. Then the food covered with dirt for a couple of hours until it's cooked.
Portable Ovens
A bunch of different kinds of portable ovens existed in the Classical period, which probably started out as pottery vessels and then grew from there. There seem to be two kinds of things people call "portable ovens." Cooking under a bell-shaped baking cover that is placed on top of hot coals until the bell is hot enough to cook food in is basically the opposite of a pit oven, but it's "portable" the way a modern campfire "Dutch oven" is. Here's a neat report of someone actually trying it in the modern day. There's also a version the Greeks used where the fire doesn't touch the ground.
To see how I use this kind of research, check out my story Beetle Siege, which features a priestess of the Gardener defending food stores from magical attack... with only an incompetent acolyte for help.