01 - Combine cold water and lemon juice in a mixing bowl to prevent apple browning.
02 - Thoroughly wash and dry the apples. Using a sharp knife or mandoline, slice apples crosswise into 1/8-inch rounds. Remove seeds and cores from each slice.
03 - With a small paring knife or mini cookie cutters, carefully carve Jack-o'-Lantern faces into the apple slices as desired.
04 - Soak apple slices in lemon water for 5 minutes. Drain and pat each slice very dry with paper towels.
05 - Place apple slices in a single layer in the air fryer basket, ensuring no overlap. Work in batches if necessary.
06 - In a small bowl, mix cinnamon and sugar if using. Lightly sprinkle the mixture over the apple slices.
07 - Set the air fryer to 300°F and cook for 12–15 minutes, flipping halfway. Check frequently for crispness and coloration. Chips should be golden and crisp, but not burnt; thicker slices may require additional time.
08 - Transfer apple chips to a wire rack to cool completely and crisp further. Serve once fully cooled.