Preheat the oven to 175°F.

Line two large baking pans with parchment paper and place a wire rack on top of each pan.

Slice the 3 navel oranges into thin slices, removing the ends where the slices are mostly pith.

Lay the slices out between layers of paper towels and press to absorb as much of the juice as possible.

Arrange the orange slices on the wire racks and bake for 1 hour.

Flip the slices and bake for an additional hour.

Flip again and bake for 1 more hour for a total of 3 hours.

Check the slices after 3 hours; transfer any fully dried slices to a plate.

For slices that appear plump or sticky, flip them and bake for another 30 minutes.

Check the slices again, remove the ones that are done, and continue baking the rest for another 30 minutes if needed. Repeat until all slices are fully dried.