'Bottom' in the Bible

These are the measures of the altar by cubits (the cubit is a cubit and a handbreadth): the bottom shall be a cubit, and the breadth a cubit, and its border around its edge a span; and this shall be the base of the altar.

From the bottom on the ground to the lower ledge shall be two cubits, and the breadth one cubit; and from the lesser ledge to the greater ledge shall be four cubits, and the breadth a cubit.

The ledge shall be fourteen [cubits] long by fourteen broad in the four sides of it; and the border about it shall be half a cubit; and its bottom shall be a cubit around; and its steps shall look toward the east.