We have had a lot of milk donations over the past seven months and it has taught me quite a bit about milk storage. I still remember the first time I thawed a bag of milk that had been frozen flat. The amount of time and water required was reduced by at least ten times what we were used to, and at that time we were feeding our boys exclusively donor milk by bottle. Between the two of them, we spent a lot of time thawing milk, and this significantly cut down on bottle prep time.
Most milk when it gets thrown into the freezer ends up looking something like this:
This hard nugget of milk takes incredibly long to thaw and its odd shape makes it a pain to keep the freezer even remotely organized. I think it often gets frozen this way so the number of ounces is easily visible with the markings on the bag.
Instead, mark the number of ounces on the outside of the bag in permanent marker along with the date and place it flat in the freezer so when it is frozen it looks something like this:
Having the milk frozen this way increases the surface area, which means when you thaw it under warm water, more of the water can touch more of the milk, helping it thaw faster. Plus its slim shape means it is very easy to store the milk upright chronologically, making it easier to follow a first-in-first-out milk-using policy (use older milk first).
This is the one of the simplest changes possible, takes zero extra time, and can make your life significantly easier.