Carefully peel off green layer from watermelon using a vegetable peeler. Save watermelon for another use. Slice rind into 1/2 inch pieces.
Boil water and 5 teaspoons salt in a large pot over medium high heat. Place rind in pot and lower heat, simmer 15 minutes. Strain and place rind in a large bowl.
Add pickling spice, ginger, cloves, allspice, and cinnamon to a double layer of cheesecloth. Secure edges of cheesecloth together with string. Add cheesecloth bag, remaining 1 teaspoon salt, sugar, and vinegar to a pot and let boil, mixing until sugar dissolves.
Spoon hot vinegar mixture over rind. Let cool to room temperature. Wrap and refrigerate 12 hours.
Drain rind mixture through a fine chinois over a pot. Place solids back into bowl. Boil liquid and spoon over solids. Refrigerate again for at least 8 hours.