Carefully slice apple into very thin slices, approx. 1/8" thick. Alternatively, use a mandoline to slice the apple.

Add apple slices to a large bowl and sprinkle over cinnamon. Mix thoroughly.

To cook in the air fryer: lay apple slices in an even layer in the air fryer basket (you will likely need to do a couple of batches to cook the entire apple). Cook in the air fryer at 350 deg F for 10-12 minutes or until the apple chips are golden brown. Remember to check the apple slices 2-3 times during the cooking process, so you can reposition them or move them back into a single layer.

To cook in the oven: preheat the oven to 300 deg F. Line or lightly grease two cookie sheets. Lay the apple slices on the cookie sheets in a single, even layer. Bake for 40-45 minutes until the apple slices are golden brown and crispy.

After cooking, remove the apple slices from the air fryer basket/cookie sheets and transfer to a plate to continue crisping up for a few minutes, or till cool enough to handle with your fingers.

Enjoy immediately!