Preheat oven to 200°F. This low temperature helps dry the oranges slowing and prevents them from burning.
Using a sharp knife, slice each orange thinly into approximately 1/4 inch rounds. Be sure to keep them uniform in while slicing to help dry them evenly.
Place a layer of parchment paper on a baking sheet and lay the oranges in a single layer. Make sure they do not overlap.
Bake for 2-3 hours, flipping each slice halfway through the bake time. You'll know when they are done by the oranges being dry to the touch and slightly translucent. Be sure to check on the periodically.
Once fully dry, remove from oven and allow them to cool before handling.
Thread a large needle with twine or ribbon, and carefully weave the needle through the top of each orange slice.
Once all your slices or threaded, tie off the ends and twine and hang your garland where you'd like to add a touch of holiday warmth!