Wash the oranges thoroughly
Pat them completely dry
Preheat the oven to 200°F to 250°F
Slice the oranges into thin, even rounds
Remove any seeds
Line a baking sheet with parchment paper or a cooling rack
Arrange the slices in a single layer
Bake for 2 to 4 hours, flipping occasionally
Check regularly to prevent burning
Remove when the slices are dry and no longer sticky
Let the slices cool completely
Store in an airtight container