I've only brewed 2 extract batches but here is my method. A few days before brew day boil some water with a bit of Campden, cool and freeze. I freeze 2 quarts in a clean and sterilized Lock n Lock container as well as some more in 5 clean and sterilized 2 cup Ziploc freezer containers. I take containers out of the freezer for 30 minutes or so before I need them so they melt enough to slip easily out. I add the 2 quart to the bottom of the fermenting bucket and pour the hot wort over. I then top off with as many of the 2 cup portions as I need.