Step 1: Preheat the oven to 200°F (95°C).
Step 2: Wash the oranges thoroughly and slice them into thin rounds, about 1/4 inch thick.
Step 3: Line a baking sheet with parchment paper and arrange the orange slices in a single layer.
Step 4: If using, sprinkle sugar or cinnamon over the orange slices.
Step 5: Dry the oranges in the preheated oven for about 4 to 6 hours, checking every hour and flipping halfway.
Step 6: Once dry, let the orange slices cool completely before storing them in an airtight container.
