It is the custom to stand while performing this mitzvah.
4.Remove a small piece from the dough, lift it, and say:
The piece of dough can be of any size. The custom is to separate a kazayit – 28 grams (approximately one ounce), or the size of a ping-pong ball.
5.Burn the separated dough or wrap it in two layers and discard it.
It is preferable to burn the piece of dough that has been separated, but not in the oven. If the challah is burned on the gas range, it should first be well wrapped in aluminum foil so that the dough does not touch the grate. Another option is to place the piece of dough inside a tin-can and burn it on a lit gas range.
If burning the challah cannot easily be done, it may be wrapped in two layers of a material such as aluminum foil or plastic bags and discarded.