My best suggestions is to cut off the top and bottom of your squash to provide a sturdy surface to rest your squash on. If you do not want to consume the peel of your kabocha squash, you can peel it off with a vegetable peeler or carefully glide your knife from top to bottom of the squash to discard the peel. Once peeled, you can then cut your squash in half and scoop out the seeds before cubing it.