oven
To one side of the pistrinum is the oven. You're able to get a good look at it after the woman in front of you got her bread. It is quite open in the front, able to hold many loaves of bread simultaneously. From your place in line, you can feel the heat and can only imagine how warm the cooks must be. It appears that the oven is a recent addition to the room, probably after the earthquake with the tricinium was converted to this pistrinum.