Preheat oven to 200 degrees. Using a sharp knife or mandolin, slice apples thinly. Discard seeds. Prepare a baking sheet with parchment paper and arrange apple slices on it without overlapping. Sprinkle cinnamon over apples. Bake for approximately 1 hour, then flip. Continue baking for 1-2 hours, flipping occasionally, until the apple slices are no longer moist. Store in airtight container.