Any tips on how to close up the Avent disposable liners? (Am I just a moron?)

The clips they provide are narrower than the bags. So, I sort of fold the corners over to make a narrower 'neck', then clip them. This is goofy, and fails if there's more than 5 oz in the bag. It also will leak in the refrigerator. If I am freezing them, the milk usually freezes before it leaks too much.

Is this typical, or am I doing something wrong?