Preheat oven to 250
Slice Oranges in thin slices using a knife or mandolin.
Line two cookie sheets with foil and spray lightly with cooking spray.
Place orange slices on pans in a single layer.
Sprinkle orange slices with sugar (skip this step if you are making a wreath)
Let them dry in the oven for 2 hours +, check on the orange slices towards the end to ensure they do not burn.