Sterilize 1 quart mason jar. Coat the bottom of the jar with a thin layer of salt.
Cut each lemon lengthwise into quarters to within about 1/2" of the base, keeping attached at the stem end.
Holding a lemon over a bowl, press a generous amount of the salt into the exposed flesh. Close up the lemon and roll it in more salt to coat the skin. Put the salted lemon in the jar and continue with the remaining lemons, pushing each lemon down tightly to release some of the juice and fill all the space. Pack jar to within 1/4" of the top. If the released juices do not cover the lemons, top it off with more squeezed lemon juice before closing the jar.
Keep the jar in a cabinet for four weeks, turning the jar every day.
To use: rinse the amount of lemon needed under water. Store the opened jar in the refrigerator. The lemons will keep six months, as long as they are completely covered with juice. If the juice level falls to low, top it with more fresh lemon juice.