Use a
mandolin or knife to cut the apples as thinly and evenly as possible. Brush off any seeds or stems. Lay out the apple slices in a single layer so they aren't overlapping. If desired sprinkle with cinnamon or pumpkin pie spice, which you can mix with a bit of white sugar for extra sweetness if you wish. Bake for 1 1/2 to 2 1/2 hours until apple slices feel dry and leathery. Turn off the oven and crack open the oven door, and let chips cool completely in the oven to crisp up.