Use distilled or filtered water
Boil the water, then let it cool
Pour the water into a clean insulated cooler or directional-freezing mold
Freeze it slowly in a freezer
Leave the top exposed if using directional freezing
Remove the ice before it freezes completely through
Cut away the cloudy bottom and sides
Store the clear ice in a sealed bag in the freezer
Use a clean, covered container to prevent freezer odors