In general, it takes three to four hours to make ice cubes. Leaving them in the freezer overnight to make sure they are solid all the way through is recommended.
Using hot water to make ice cubes can make them freeze faster and look better. This phenomenon is called the Mpemba effect. If equal volumes of warm and cold water are frozen with the same external temperature, the time it takes for the warm water to freeze is less than the time it takes the cold water to freeze. Hot water also holds less dissolved oxygen, resulting in clearer ice cubes.