No Ice Cream Maker? This is a pretty creamy base recipe, so you can get away with a couple of other methods. One is to freeze the peach slices solid then puree with the other ice cream ingredients. It should be quite thick. Stir in the crumbles, pour into a chilled container, cover, and freeze.
Paleo Option: Substitute finely ground coconut sugar for the brown sugar in both the crumble and ice cream. Substitute unsweetened shredded coconut for the quick oats and ⅓ cup coconut flour for the oat flour in the crumble. Yes, it will have a coconut vibe, but trust me, it's delicious!