Scrub the lemons with a vegetable brush and dry them off.
Cut off the little rounded bit at the stem end if there’s a hard little piece of the stem attached. From the other end of the lemon, make a large cut by slicing lengthwise downward, stopping about 1-inch (3 cm) from the bottom, then making another downward slice, so you’ve incised the lemon with an X shape.
Pack coarse salt into the lemon where you made the incisions. Don’t be skimpy with the salt: use about 1 tablespoon per lemon.
Put the salt-filled lemons in a clean, large glass jar with a tight-fitting lid. Add a few coriander seeds, a bay leaf, a dried chili, and a cinnamon stick if you want. (Or a combination of any of them.)
Press the lemons very firmly in the jar to get the juices flowing. Cover and let stand overnight.
The next day do the same, pressing the lemons down, encouraging them to release more juice as they start to soften. Repeat for a 2-3 days until the lemons are completely covered with liquid. If your lemons aren’t too juicy, add more freshly-squeezed lemon juice until their submerged, as I generally have to do.
After one month, when the preserved lemons are soft, they’re ready to use. Store the lemons in the refrigerator, where they’ll keep for at least 6 months. Rinse before using to remove excess salt.
To use: Remove lemons from the liquid and rinse. Split in half and scrape out the pulp. Slice the lemon peels into thin strips or cut into small dices. You may wish to press the pulp through a sieve to obtain the flavorful juice, which can be used for flavoring as well, then discard the innards.