Pre-heat oven at 225 °F.
Prepare 2 cookie sheets with baking paper (parchment) or a silicon mat.
Slice apples using a mandolin (or a very sharp knife) starting from the bottom. There is no need to remove the core or seeds.
Spread the slices on the cookie sheet and sprinkle them with cinnamon.
Bake for an hour and a half to two hours. The time in the oven will determine the consistency of the chips: a longer cooking time yields a crunchier chip.