Preheat the oven to 250ºF. Place baking racks in upper and lower thirds of the oven. Line 2 rimmed baking sheets with parchment paper.
In a small bowl combine the sugar, cinnamon and salt; set aside. With a sharp knife or mandoline, slice the apples as thinly as possible. In a large bowl toss together the apple slices and lemon juice. This will help prevent the apples form oxidizing. Place the apple slice on the parchment in a single layer, trying not to overlap too much. Sprinkle the cinnamon sugar evenly over the apples.
Bake the apples for 1 hour. Remove from the oven and turn the apple slices over. Return baking sheets to oven on opposite racks. Bake for 1 more hour. Remove from the oven and let cool on a wire rack. Store in an airtight container. Enjoy!
Notes
*I don't peel or core the apples. Once sliced, the seeds pop right out and I like the curled edges that the peel makes when dried. But, feel free to peel or core to your own preferences.