When storing breast milk in storage bags, do you prefer to freeze them as a flat bag or standing up? If flat bag, when defrosting, what method do you take on to ensure bag doesn't leak?

My colleague freezes the bag by laying it flat, this helps maximize storage space in the freezer. To thaw, she will first shift the required amount from the freezer to the fridge the night before. To warm up the milk, she will run warm water over the bag. She has only encountered a "leaky bag" couple of times. But those were due to holes in the bag. So she simply placed the bags for thawing in a bowl to prevent it from spilling.