Preheat oven to 200 degrees. Line 2 baking sheets with parchment paper.
Thinly slice apples using a mandolin slicer (or by hand if you are up for the challenge). Toss out any unwanted seeds or apple pieces. Lay them flat on lined baking sheets, and evenly sprinkle with cinnamon.
Bake at 200 degrees for approximately 2 hours. Loosen the apples from the parchment paper with a spatula so that they will get nice and crispy.