Using a sharp knife, carefully cut the oranges into ¼-inch slices. Try to keep the slices even so they dry at the same rate.
Lay the slices out on a paper towel and gently press to absorb excess moisture. This step helps prevent sogginess and speeds up drying.
Preheat the oven to 200°F (90°C). Line a baking sheet with parchment paper and place orange slices in a single layer. Bake for 2–3 hours, flipping every 30 minutes, until the dehydrated orange slices are dry and slightly crisp at the edges.