The Torah (Vayikra 6:12-15) describes the chavitin, a type of minchah offering that was brought daily (and paid for) by the Kohen Gadol. The chavitin consisted of a prescribed amount of flour, water, and oil that were kneaded together, scalded in boiling water, baked, and then fried with oil.Twelve loaves of chavitin were prepared each day, half of which were offered in the morning and half in the afternoon. The loaves were brought on every day of the year, along with the daily Tamid offering, and were completely burned on the outer Mizbeyach.
The work of preparing this minchah offering was carried out in the Chamber of the Makers of the Chavitin (#21 in the diagram), located along the eastern wall of the Azarah to the south of the Nikanor Gate (#18). A chamber specifically within the consecrated confines of the Azarah was used for this purpose since the chavitin were sanctified and would become invalid if removed from the Azarah. To avoid crowding the Azarah any more than necessary, this chamber was built [partially] within the wall of the Azarah.
The Chamber of the Makers of the Chavitin was conveniently located right around the corner from the Chamber of the Oils (#14), where the oil and flour for the minchah offerings were stored. Because this latter chamber had to be accessed so frequently during the course of the avodah, it had its own entrance into the Azarah (#26) through which the ingredients could be brought without delay.