There are a few ways to make a mold for ice balls. One way is to use a loaf pan. Cut the loaf pan in half and then cut out a hole in the middle of the pan. Freeze the pan overnight and then use it to make ice balls. Another way is to use an ice cube tray. Make sure that the tray is big enough so that there are at least two inches of space between the cubes and the edge of the tray.