Preheat oven to 225F (110C) and line 2 large baking sheets with parchment paper.
Whisk 3 Tbsp icing sugar with 3 Tbsp maple syrup and set aside. Sift remaining 3 Tbsp icing sugar evenly onto lined baking sheets.
With a mandolin or other manual slicer cut apples crosswise into paper-thin slices.
Arrange apple slices in one layer on sheets and brush with maple syrup mixture.
Bake slices about 2 hours (rotate pans halfway through cooking), or until slices are pale golden and starting to crisp.
Brush apple slices with remaining 3 Tbsp syrup and sprinkle with chopped pecans and cinnamon.
Bake an additional 20 minutes. Immediately peel apple bites off parchment and cool on a rack.
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