The exterior skin of the squash is very tough, but there is a trick that will make cutting it much easier. With a sharp knife, make a few slits in the squash where you plan to cut, like you are making a dotted line around the outside. Microwave the entire squash for 2-3 minutes, then allow it to cool enough to handle it. You can also just microwave it, skipping the slit making process. At this point, the squash skin will be soft enough to cut easily along your pre-cut lines!