Set oven to 200°F (95°C) with convection mode on. Prepare a baking tray by lining it with parchment paper; leave it aside.
Slice the citrus using a mandoline or a very sharp knife into pieces no thicker than 1/4 inch. Slices that are thicker require more cooking time.
Place the citrus slices on the tray lined with parchment and bake for 3–6 hours, depending on the size of the citrus. Lemons and limes need the least time, then oranges; grapefruit requires the most.
About 2 hours into baking, turn the citrus over so the side that touched the parchment is now facing up. Also rotate the tray so that the pieces nearest the oven glass are moved to the back. Continue this every 2 hours as needed.
When the citrus is completely dry and snaps when touched, take it out of the oven and allow it to cool fully.
Serve as a garnish for cocktails, sprinkle on baked goods, or process into citrus sugar. Enjoy!