• Use an apple corer to core the apples if you prefer. Then using a very sharp knife or a mandolin, slice the apples widthwise into ⅛ inch thickness.
• Transfer the apple slices to a large bowl and sprinkle with cinnamon. Toss well to combine.

For Oven

• Preheat oven to 200°F. Line a baking sheet with parchment paper.
• Arrange the apples in a single layer on the prepared baking sheets. Bake in the preheated oven until the apples are crisp to the touch, about 3 hours, flipping halfway through.
• Transfer the apples to a wire rack and allow to come to room temperature, which will help them get more crisp.

For Air Fryer

• Preheat oven to 300°F.
• Arrange the apples in a single layer in the air fryer, being careful not to overlap them. Air fry until they are crisp to the touch, about 15 minutes, flipping a few times.
• Transfer the apples to a wire rack and allow to come to room temperature, which will help them get more crisp.