Sterilise your jar using either food safe steriliser or by washing in warm soapy water and leaving to dry in your oven on a low heat.
(If you have not been able to source unwaxed lemons, run them under hot water and scrub to remove the wax.)
Cut your lemons into wedges. (For a pretty look you can leave them in tact at one end but this is not essential and you may struggle to fit the whole lemon through the neck of your jar).
Sprinkle each lemon wedge with 1 teaspoon of salt and place into the jar (adding any spices to the jar at periodic intervals).
As you add the lemon wedges to the jar push them down to release their juices and to ensure they are packed in tightly (a cocktail muddler comes in handy for this!).
Once the jar is full, push them down again to release their juices and to ensure there are no air bubbles between the lemons. (The jar should now be full of lemons and lemon juice).
If the lemons are not quite submerged, add more lemon juice to the jar along with a final teaspoon of salt.
Before closing the jar, use a glass weight or a ziplock bag filled with water to ensure that the lemons do not rise above the level of the juice.
Close the jar and leave in a cool, dark place for 3 months before opening.
During those three months, try to remember to give the jar a shake roughly once a week.
Once opened, the preserved lemons should be stored in the fridge and will last several months (if you don't eat them before!).