The first day
1. This is the toughest part of the process. Cut the watermelon rind into manageable chunks. Scrape all the remaining red watermelon meat from the inside of the rind. Then pare off the hard green skin of the outer rind with a small knife. It’s not difficult but it takes a while. Cube the rind into bite-size pieces.
2. In a large bowl, dissolve the salt in the water. Transfer the rind cubes to the salted water. Find an out-of-the-way corner of your kitchen for the bowl and then weight the rind down with a plate to keep it submerged. Soak the cubes for about 24 hours.
The second day
3. Combine all the remaining ingredients in a large saucepan and bring them to a boil, simmering the syrup for about 5 minutes.
4. While the syrup simmers, drain the cubes, rinse them, and drain them again. Rinse the bowl the cubes were soaking in and return the cubes to the bowl. Pour the hot syrup over the cubes, return the bowl to its original resting place, cover it lightly, and let it sit for another 24 hours, more or less.
The third day
5. Sterilize 5 to 6 pint canning jars according to the manufacturer’s directions.
6. Pour the cubes and syrup into a large pan and bring the mixture to a boil. With a slotted spoon, pack the cubes lightly into the prepared jars, dividing the lemon slices and spices equally among the jars. Pour the syrup over the cubes, covering them but leaving about ½ inch of headspace. Seal.
7. Process the jars in a boiling water bath for 10 minutes. Allow the pickles to sit for at least 1 week, and preferably several weeks, before serving.