Using a sharp paring knife, remove the hard green exterior from each piece of watermelon rind. Cut pieces into 1-inch squares.

Make a cold brine by dissolving salt in cold water. Pour the brine over the watermelon rind and let stand for 5-6 hours in the refrigerator.

Drain the watermelon rind and rinse well with cold water over a colander.

Cover the rinsed watermelon rind with more cold water and let stand for 30 minutes. Drain.

Place the watermelon rind in a large saucepan and sprinkle with dried ginger. Cover with cold water and cook until fork tender, about 10 minutes. Drain.

In a large saucepan, combine sugar, lemon juice, and 7 cups of water. Boil for 5 minutes and then add watermelon rind and cook for 30 minutes.

Add sliced lemon pieces and continue to cook until the watermelon rind is clear.

Prepare jars for canning. Ladle hot preserves into jars and cover with hot syrup, leaving 1/4-inch headspace. Wipe sides and rim of jars, apply two-piece metal canning lids.

Load jars into hot water canner and process for 10 minutes, adjusting for altitude.

Remove jars from canner and transfer to a clean surface lined with a kitchen towel; leave 1 inch of space between each jar.

Let the jars come to room temperature, about 12-24 hours, and then check seals on each jar. Unsealed jars should be stored in the fridge, sealed jars can be kept in a cool, dry place away from direct light for up to 18 months.