The quest for perfect ice is older than mankind, and slightly younger than the quest for perfect whiskey. One of those problems can be solved for you with a stroke of genius.
But why is ice cloudy in the first place? Cocktail Chemistry explains that impurities in water are the last to freeze, and those impurities are what cause ice to look ugly and opaque. The free and painless solution is to use a cooler. Since the insulated sides cause the water to freeze from the top down, the impurities sink to the bottom and you’re left with crystal-clear ice (and some crappy water). The same method works just fine with spherical ice moulds as well.
From there, a serrated knife and a small mallet will allowed you to carve the ice into big cubes, small cubes, or spears for highballs. Neat!