72:21 Continuing to speak of methods of keeping food warm before modern technology, let’s say that someone insulated a pot of coffee on Friday for use on Shabbos by placing it in a pit and covering it with pillows and blankets. If he wants to insulate it in sand, which is a substance that adds heat, he may not completely enclose the pot. This is true even if he wants to cover the exposed portion with a blanket. Rather, the pot should be only one-half or one-third covered with sand, with the remainder of it left exposed. One may then place a board or another pot over the pit so that there is an air space between pot and this covering. This covering may then be covered with pillows and blankets.
72:22 Close to the beginning of Shabbos, a person should nicely ask the members of his household whether the portion of dough called challah has been separated(, the eiruv has been made, and the tithes separated – Orach Chaim 260:2). He should then instruct them to light Shabbos candles (and to refrain from performing acts of labor – Mishnah Brurah 260:14).