I put some of the tank water in a glass and drop the frozen cubes in the water to thawout a bit. You can then break them up a bit or just drop them in whole (which I do) into your tank. Store the cubes in a paper bag in the freezer.
I precut my cubes into 4ths. and then each piece in half. I just throw them in frozen and they last all of 30 seconds. I've recently put in a couple of extra thawed out pieces because my foxface isn't as quick as the rest. Was thinning out first couple of weeks. Now looks better.