Dehydrating citrus is super-easy, but it does take a long time. So if your craft (or whatever) calls for it, make sure you give yourself at least five hours, or better yet, a day to prepare it.
There are a few ways you can do dry them out. You can do it by simply laying them out to air-dry, I don’t find this to be the best way. It can attract fruit flies and mold. You can use your fancy food dehydrator. I would do this if I had one!
My way is to use my oven.
Instructions for Dehydrating Citrus in your Oven
Preheat your oven to 400F
Wash and dry your citrus.
Then slice it as thinly as you can manage, and still have it fairly even. This is much easier to do with lemons and limes, but with a sharp knife and some care, it’s not too difficult with the oranges and grapefruit.
Place a drying rack on top of a cookie sheet. This allows the air to circulate beneath the citrus to dry it out faster and more evenly. This also saves you from having to flip them every hour or so.
Put your citrus onto the rack and into the oven.
Bake until they are dry and not the slightest bit moist. Depending on how thick you ended up making your slices, this can take between 2 and 8 hours. Limes are usually done in 2 hours, they dry out really fast. Make sure you check the citrus from time to time and pull out the ones that are done or you will burn them!
Enjoy your dehydrated citrus!