Preheat oven to 250 degrees and line 2 baking sheets with unbleached parchment paper.
Arrange the apple slices on the baking sheets in a single layer and sprinkle with cinnamon.
Place the baking sheets into the oven on the center rack and bake for 1 1/2 hours.
Flip apples, sprinkle with cinnamon and bake for another hour.
Remove from the oven and let cool completely.