It’s not hard, it just isn’t particularly efficient or convenient. The standard method is to use a bunch more water that you want to become actual ice, make it in large insulated blocks, then chop at the end. I have a little insulated tray that makes two at a time. They come out pretty clear, but at least half the water used is essentially waste to create a clear cube. The top half being still ice, but full of little bubbles, not clear. If I was throwing a party, as people are want to do on summer weekends, and I wanted many many big clear ice cubes then I’d seriously consider buying a box load.

To get clear ice you have to freeze it slowly, basically just at the freezing mark (32°C/0°F) which is a warmer temperature than most people have their freezer set to. It’s not difficult in an objective sense, it just requires rubbing a couple of brain cells together and a tiny morsel of effort which is apparently more than a lot of people can muster.