S.L.
I hated ice cube trays! First off, my boys ate 9 at a time, so the volume was way too small. I bought baby food in jars when they were on a super sale, or when I needed some for trips (when refrigeration wasn't available). Then I snagged some of the cardboard "trays" from the baby food at the store. That helps the little jars stack neatly in the freezer.
To label them, I simply wrote on the jar with a permanent marker. The marker stays on in the freezer, but washes off in the dishwasher. Perfect!