Slice apples thinly crosswise, using a sharp knife or a mandolin slicer (about ⅛" thick).
Line a cookie sheet with parchment paper or a Silpat sheet, and arrange slices in one layer, as many as you can fit on the cookie sheet.
Bake for 1 hour, flip slices over and bake for another hour or until all slices are just getting crispy and very lightly browned. Continue baking as noted above.
Optional: before baking, brush the first side of the apple slices lightly with maple syrup and sprinkle lightly with cinnamon. Bake for an hour, then flip and brush the other side with syrup and sprinkle again with cinnamon.
Recipe by The Framed Table - Food, Drinks & Photography at https://theframedtable.com/2012/11/07/apple-chips/