I suppose this verse describes the entrance into the south chambers, that it was on the east point, and that whose would go into them must go up the stairs (which probably were winding stairs) at the east end of these buildings, whose front was toward the south.
Related Commentaries of Ezekiel 42:9
Ezekiel 42:9
9 And from under these chambers was the entry on the east side, as one goeth into them from the utter court.