Cut the watermelon rind, from which you have removed the outer green rind and inner pink flesh, into 1-inch cubes. You should have 7cups.
Place the watermelon rind in a large container with the kosher salt and 3 cups of water. If necessary, add more water to cover the rinds. Soak overnight.
Drain and rinse the watermelon rind.
Place rind in large saucepan. Cover with cold water. Bring to a boil, lower heat, and then simmer until just tender when pierced with the tip of a knife, around 10 minutes.
While the rind is cooking, combine the sugar, vinegar, cinnamon, whole cloves, and 1 cup of water in a nonreactive stock pot or Dutch oven. Bring to a boil, then lower heat and simmer for 10 minutes.
Carefully add the drained watermelon rind, lemon slices, and maraschino cherries to the syrup. Simmer until the watermelon rind is translucent, about 30 minutes.
Fill half-pint jars with the hot watermelon rind and syrup, leaving ½-inch headspace. Close jars with lids.
Process jars in a boiling water bath for 5 minutes.
Carefully remove the jars to a rack and allow to cool.
Serve.
Note: After opening, pickles will keep for a few weeks, refrigerated. Unopened jars of watermelon pickles will keep for at least a year.