This is something else I stumbled upon while experimenting with different containers to use for freezing ice. I have an insulated sleeve designed to hold one of those Nalgene bottles that were all over the place until the fancy aluminum ones took over. The thing is, it also perfectly fits the style of take out container used at almost every Thai and Indian restaurant I've ever been to. The cooler method is great and I use it regularly, you get more ice. But, for sheer convenience and ease this sleeve can not be beat. And it takes up much less room in the freezer. Steps are the same. Fill your plastic take-out container with water, slide it into the sleeve, and freeze it. When it's ready to go, run it under cold water for a second. The ice will slide right out. Then just use an ice pick to chop off the cloudy section.
Takes about 5 seconds and then you have a big chunk of clear ice, plenty to carve a sphere from if that's where you're headed.
That knife's edge has been blunted with a file but is still sharp enough to work on ice.