Heat the oven to 225°. Line two large baking sheets with parchment paper. With a sharp knife or mandoline, thinly slice apples. (The thinner the slice, the crispier the chip.) Remove the seeds with a paring knife. Place the slices in a single layer on the prepared sheets. Stir together cinnamon and brown sugar. Sprinkle half the mixture onto the apples. Bake for 1 hour. Use tongs to flip the slices and sprinkle with the remaining cinnamon sugar. Bake for 1 hour more. Turn the oven off, but leave the apples inside for another hour to crisp. Let them cool, then store them in an air-tight container until ready to eat.