Peeling the peaches for peach crisp is optional but recommended. There is nothing wrong with eating the skins, but some eaters prefer the smooth texture of skinless peach slices. If peeling the peaches is beyond the realm of your interest, go with frozen peach slices instead. They are already peeled, pitted, and sliced, and you can use them in this recipe the same as fresh (no need to thaw; baking time stays the same).