I found myself in a newly rented third floor apartment in the thick of the summer. There were no ice cube trays in the freezer. Luckily, I had been to the grocery store to buy eggs, and there was an integrated egg container in the refrigerator.
So I stashed the eggs into the fridge and improvised ice cube trays out of the plastic egg cartons. It worked quite well. They are slightly flimsy when handling them with water. Not bad, though. And the draft angle is quite steep, so the ice releases with a gentle push from below.