Wash your lemons thoroughly & set them in a colander in the sink to drain. You will need 8-10 lemons for each 1 quart canning jar that you use.
Place your canning mat in the bottom of a deep pot. If you don’t have a canning mat, line the bottom of the pot with a clean cloth dishtowel. This will keep the jars from bumping against each other when you sterilize them.
Stand the quart jars in the pot with their open ends facing up.
Fill the pot with water so that the jars are completely covered. Bring the water to a boil. Lower it to a rolling simmer & cover the pot. Let the jars sterilize for 10 minutes without disturbing them.
Lay a folded dishtowel on the counter. Remove the jars from the water with your canning tongs & place them on the towel, open side up. Never put hot jars directly onto a cool surface like a bare counter because they may shatter.
Drop the lids and rings into the boiling water & turn off the heat.
Slice both ends off of each lemon & cut the lemons into 4-6 wedges each.
Lay the wedges out on a platter or a length of waxed paper & lightly salt them with the Kosher salt.
Fill the bottom of the jars, once they have cooled enough to touch, with ½ c. Kosher salt.
Fish the lids & rings out of the hot water with the canning tongs & set them on the dishtowel with the jars to cool.
Squeeze each lemon wedge gently as you pack them snugly into the jars.
Fill the jars with lemon juice so that the lemons are just covered. Sprinkle another layer of salt on top.
Wipe any excess salt or lemon juice off of the mouths of the jars with a clean dishtowel. Seal the jars with the sterilized lids & rings.
Let the jars sit at room temperature for 24 hours & then turn them upside down. Let them sit for another 24 hours, then turn them right-side up & place them in the refrigerator.
Leave the jars in the refrigerator for three weeks, occasionally turning them upside down for a day or two.
To use the lemons, pick one out & wash off all of the salt. Discard the seeds & pulp & grate or finely chop the lemon rind.
Add visual interest as well as flavor by adding mint sprigs, rosemary, sage, thyme, peppercorns, whole cloves, whole coriander seeds, or cinnamon sticks to your preserved lemons when you pack them into the jars. Experiment by adding different combinations of herbs & spices.