Preheat the oven to 400 F.
Slice the potatoes on a mandolin or with a sharp chef's knife, in ⅛ inch rounds. Place in a large bowl and evenly coat with olive oil, salt, and pepper.
Lay the potatoes flat in an oven-safe dish and top with garlic and rosemary.
Bake for 40 minutes, stirring or flipping potatoes at 20 minutes, if necessary. Serve hot!