Submerge the prepped rind in the salted water and let sit overnight at room temperature. Use 1 tablespoons of salt for every 2 cups of water, making sure the rind is completely submerged. I usually use about 6 cups of water and 3 tablespoons of salt, but it depends on the size of your watermelon.
The next day, bring the rind and salt water to a boil. Simmer for 10–15 minutes until the rind can be easily pierced with a fork. Drain well.
In a saucepan, bring the sugar, vinegar, cloves, and cinnamon to a boil, stirring until the sugar dissolves. Pour the hot syrup over the drained rind. Cover and let stand overnight. To make sure it's submerged, you can cover it with a sterilized weight.
Drain the liquid back into your saucepan, reserving the rind. Bring the syrup to a boil again, then pour back over the rind. Cover and let stand overnight once more.
On the third day, pour both the rind and syrup into the pot together. Bring to a full boil.
Transfer the hot rind and syrup into sterilized canning jars (leaving ½-inch headspace). Cool and store in the fridge. Or, seal and process in a hot water bath for 10 minutes.**
Notes
* I use a 8-12 lb. watermelon.** I almost never can/preserve these, but you can process them in a water bath on a rack after they're jarred for 10 minutes. Cool overnight on towels to room temperature.Easily cut in half, which I do often. If cutting in half, don't quite cut the sugar/vinegar/spice mixture in half.