Halakhah sa Exodo 27:1: Mishneh Torah, Leavened and Unleavened Bread, Mishneh Torah, The Chosen Temple, Sefer HaMitzvot & Kitzur Shulchan Arukh

And the Sages forbade eating chamets from the beginning of the sixth hour so that one not touch a Torah prohibition. So from the beginning of the sixth hour, chamets will be forbidden for eating and benefit the whole sixth hour from the words of the Scribes (rabbinically); and the rest of the day from the seventh hour and onward from Torah writ. [In addition], we may not eat chamets in the fifth hour, [as a] decree on account of a cloudy day lest he mistake the sixth hour [for] the fifth hour. But it is not forbidden for benefit in the fifth hour. Hence we suspend priestly tithe and thanksgiving bread and that which is similar to them of chamets which is consecrated - we neither eat [it], nor burn [it] until the sixth hour arrives and we burn it [then].

The Altar that Moses made, that Solomon made, that the returnees of the [First] Exile made, and that will be made in the future are all 10 cubits high, and that which is stated in the Torah: "and three cubits its height, that is the place of the pyre alone (above the ledge of the Altar). And the dimensions of the Altar that the returnees of the Exile made and the one that will be built in the future are 32 cubits by 32 cubits.

The four corner-pieces of the altar, its base, and its squareness are all essential and any altar that does not have corner-pieces, a base, a ramp, and squareness is invalid for they are all essential, however its length, width, and height are not essential as long as it is not less than one cubit [wide] by once cubit [long] by three cubits [high] like the pyre-space of the Altar in the desert.