My mum makes these every year for Christmas and it makes the kitchen smell wonderful. Whether you're using them for wreath garnishes, wrapping decorations, cocktail or dessert garnishes, a flavour addition to a hot herbal tea or even just to dip in chocolate and eat - these are absolutely beautiful and can last years. I don't have a dehydrator so you need to set your oven to a very low heat and allow a few hours for this. I have them in the background when I've got a day working from home. You can also use other citrus fruits such as grapefruits, lemons or limes.
Preheat a fan oven to 90C and line a few trays with greaseproof paper.
Use a sharp knife to slice the oranges into very thin ( less than 1cm) slices. The thicker they are, the longer they will take to bake.
Lay your slices in a single layer on the baking sheets, leaving a small space between them, then bake on the low heat for around 4 hours, turning them over every hour. Smaller slices or fruits like lemon/limes take the least amount of time whilst larger slices and fruits like grapefruit can take up to 6 hours.
Slices are ready when they are firm, feel brittle and there's no more moisture in the segments. Once they're ready, remove them from the oven and lay them on a cooling rack where they will cool. I do this in batches starting with the small slices that are ready first (~3 hrs) and check every 20 minutes or so as the others continue to bake, until they're all done. They should be brittle enough to 'snap' once dried.
Once completely cooled, I store mine in large jam jars until I need to use them.