Muffin tins actually hold way less than you'd think, each cup is only about half a cup of rice. So if you're freezing a full batch you might end up with like 12 little pucks when you could've fit it all in one flat bag. Not saying the tin thing is sad, it's just more work than it needs to be. The real trick is spreading the rice in a thin layer on a sheet pan first so it freezes loose, then dumping it in a bag.