Preheat oven to 70c.
Line a baking tray (or 2) with parchment paper and set aside.
Using a very sharp knife, thinly slice oranges into 2-3mm thick rounds as evenly as you can.
2 oranges (I used Navel oranges)
Blot the oranges slices dry on paper towels to absorb any excess juice.
Place orange slices on the baking tray(s) in a single layer without overlapping.
Bake for 1 hour, then turn the slices over and bake for a further 2 hours or until the slices are completely dry to the touch and not sticky or tacky.
Once they are dry, remove them from the oven and place them on a cooling rack.
When completely cool, store the slices in an airtight container.