1. Preheat the air fryer to 325 F. Using a mandolin, slice the apple into 1/8″ thick slices. You do not have to remove the core unless you want to, but do remove the seeds! If you don’t have a mandolin or a food processor that can evenly slice the apples, use a sharp paring knife to carefully slice the apple.
2. Once preheated, place the apples in the air fryer basket, ensuring that there is minimal overlap of the slices. Sprinkle the slices evenly with the cinnamon, and close the air fryer basket. Cook the apple slices for 10 minutes in total, pausing the cooking process roughly every 3 minutes to flip the apple slices over, pressing them down as much as possible. If you notice some slices getting crispy too quickly, change their position in the basket to the middle. Stop cooking the apple slices when they’re sufficiently crispy for you!
3. Remove the slices to a plate or serving bowl and allow to cool completely before enjoying (or enjoy them while still warm).

Leftover apples will keep at room temperature in an airtight container or plastic zip-top bag for up to 1 week. They will get softer over time!