Preheat the oven to the lowest temperature setting that’s available (about 70 C or 160 F) Line a baking tray with parchment paper.
Wash and dry three whole lemons. Cut the ends off the lemons. Then cut each into five slices about an ⅛ of an inch thick.
Place the slices spaced apart on the baking tray. Put in the oven and allow them to dry for six to eight hours. Flip them halfway through the drying time.
Remove from the oven and allow them to cool before using. They will get even harder as they cool.