Here’s how I did it:
Slice an avocado into quarters and take out the pit. Peel off the outer layer. (Here’s a short video showing the same slicing technique that I use.) Stack into a plastic freezer bag and into the freezer they go. It’s just that easy. They work great for smoothies with frozen banana’s because they have a great ice-cream like texture when blended. Single-serving slices right out of the freezer.
There is handy little tool to make this even easier: check it out here