Core and slice your apples as thin as you can (1/8 of an inch or 3 mm)
Arrange the apple slices on the parchment paper close together so you can fit as many as you can. Lightly sprinkle with cinnamon.
Bake on the lower part of your oven (away from the heating elements) for 50 minutes, then gently turn the apple slices over and bake for another 50-60 minutes. Keep an eye on them towards the last 10 minutes or so to make sure they do not burn.
Remove baking sheet or rack from oven and allow the apples to cool. The apples will come out a bit soft but will crisp up as they cool.
Notes
Gala and Pink Lady apples work great for this recipe.