An even lower equipment option I've had some success with: Just use any food container, such as an ice-cream box or tupperware. Part fill it and put in the fr

An even lower equipment option I've had some success with: Just use any food container, such as an ice-cream box or tupperware. Part fill it and put in the freezer with no lid. It will start freezing from the outside in. When it is partly frozen but before it goes cloudy, break a hole in the top of the ice to allow the trapped liquid inside to escape, and put it back in for a few more hours until it is nearly all frozen. This way you can get a big mostly clear block with a cloudy bit in the middle (you can repeat the break and freeze to get it even smaller), which you can cut up and melt off any cloudy bits with warm water.