This is my unorthodox method for making preserved lemons in just one week. The quantity of salt is to my liking, but you can always rinse the lemons before using them just as you might for capers or olives, if they are a bit too salty for your purposes.
Peel the zest from the 1 remaining lemon (reserve the zest for future use) and squeeze the juice into the jar to cover the lemon slices. Put on the lid.
Set the jar in at room temperature (65-70 degrees F). Check it in two days' time to be sure the lemons are covered with liquid and the salt is completely dissolved. If not, give it a shake. The salt will cause the lemon to release more juice.
Within 6-7 days the rind will appear glossy with a translucent quality. It will be very tender and delicious like the salty lemon pickle it is. You can choose to continue to ferment the lemons at room temperature or store the jar in the refrigerator with a note to self to use them regularly.