Use oranges that are not too ripe. Cut 1/4 inch thick. Absorb most of the juice in the slice with paper towel or a tea towel. Place slices on a cooling rack and place on a cookie sheet. Place in a preheated oven at 150 until soft and pliable. Might take 6 hours. If the edges start to curl up, flip the slices over. Hope that helps.
Jim Barry