Midrasch zu Wajikra 24:6

2) "twelve chaloth": they must be alike; "two-tenths": each one must be two-tenths (of fine flour). "the one chalah. They must be kneaded and arranged one by one. Whence do we derive the same for the two loaves (of Shavuoth)? From "the one chalah shall be." (Vayikra 24:6) ("And you shall place them in two rows, six in a row, upon the pure table before the L–rd.") And whence is it derived that they are baked two by two? From "And you shall place them." I might think that the two loaves also are baked together; it is, therefore, written "them" — They are baked two by two, but the two loaves one by one. "And you shall place them": into a mould. There were three moulds: one into which the dough was put, one (in which they were baked) in one oven, and one in which they were taken from the oven so that they not come apart.