If using whole butternut squash, trim both ends of the squash using a sharp knife. Secure the squash in your non-dominant hand, and using a sharp peeler in other hand peel the butternut squash skin. Cut the squash in half (it may help to have the squash stand upright on a cutting board). Scoop out the seeds from the inside of the squash. Cut the squash crosswise in half, then into smaller sections and lastly, into cubes.