2 medium red apples 1 teaspoon of ground cinnamon Preheat the oven to 200ºF. Use a sharp knife or mandolin to cut the apples into very thin slices. Remove the seeds and core from the middle and then arrange the apple slices on a lined baking tray. Make sure none of them overlap. Sprinkle the slices with cinnamon and place in the oven. The slices take approximately 2 – 2.5 hours to cook and you’ll need to flip them over several times so they become crispy.