Combine frozen potatoes, soup, onion, 1 cup Cheddar cheese, sour cream, butter, garlic, salt, and pepper in a large bowl. Stir until evenly combined and pour into a slow cooker.
Cover and cook on high for 3 hours, stirring once every hour. Turn slow cooker off.
Sprinkle remaining cup of Cheddar cheese over the top, cover, and let sit until cheese has melted, about 5 minutes. Transfer to a serving dish and top with crushed potato chips.