Use a large sharp chef’s knife to cut both ends off the squash. Prop the squash upright with the bottom on a flat surface and cut it in half lengthways. Make sure it’s stable on a cutting board and keep your fingers out of the way. Use a vegetable peeler or knife to remove the skin and scoop the seeds out with a spoon. With the flat side down, cut the squash into strips and then dice into 1-inch cubes.