Boyd’s Bible Dictionary:

(arch). Fixed ovens (Hos. 7:4). Portable, consisting of a large clay jar (Ex. 8:3; Lev. 26:26).

Concise Bible Dictionary:

Except in cities where there were those who followed the trade of the baker, with built-up ovens, it was customary for every household to have its own simple oven. A hole was dug in the ground and coated with clay, which hardened with the heat of the fire. Any species of grass soon dried in the sun and was then thrown into the oven to heat it. The bread was made into thin cakes which were baked by being stuck to the sides of the oven, or placed on a cover at the top. There are many instances in scripture where on the arrival of a visitor bread had to be kneaded and baked for them (Ex. 8:3; Lev. 2:4; Lev. 7:9; Lev. 11:35; Lev. 26:26; Lam. 5:10; Hos. 7:4-7; Matt. 6:30; Luke 12:28). The heat of the oven is used symbolically for rapid destruction (Psa. 21:9; Mal. 4:1).
Samaritan Passover at Mt. Gerizim. Heating the oven.