Minecraft wiki entry for Ice_farming, associated text: An ice farm consists of a large flat pan, open to the sky in an icy biome, which contains an infinite water source. Two diagonally adjacent walls will have outgrowths protecting strategic water blocks from freezing, causing a fully mined-out farm to refill with fresh water source blocks. Using light sources to protect these blocks is not recommended, due to the melt/refreeze cycle this would cause. An ice farm's footprint is 3 layers deep, and however large you want the ice layer to be. The configuration for a 7x7 farm is shown below. (Note: If you want to make the farm larger than 7x7, make an X shape with the covered water sources.)