Prepared sheet pans with parchment paper and set aside.
Slice apples thinly crosswise, using a sharp knife or a mandolin slicer.
Arrange slices on cookie sheets in one layer. Sprinkle lightly with cinnamon if that strikes your fancy! I like them plain.
Bake for about two and a half to three hours, flipping every 45 minutes or so.
Store in an air tight container.