Before heating your oven, make sure that the racks are in the upper and lower thirds of your oven. Then set the temperature to 200°F and line two baking sheets with parchment paper.
Next, wash and core the apples to get rid of the seeds. Once the apples are ready, use your slicer to slice the apples into ⅛" thick slices and set aside. Continue slicing until all the apples are used. Then layer the apples on the baking sheets and sprinkle with cinnamon before placing in the oven and baking for one hour. After an hour, swap the tray's positions so that the one that was in the upper is now in the lower and continue to bake for another hour to an hour and a half. To test if the apples are done, remove one for the oven and allow it to sit at room temperature for 2-3 minutes. This will let you see the level of crispiness.
When you have the desired crispiness, turn off the oven and allow the apples to sit in the oven for at least another hour. Keep in an airtight container for up to 1 week.