Sterilize your 1 qt glass jar canning jar (run through dishwasher, run under very hot water, use your instant pot) - just make sure it is clean.
Cut 2 slits in each lemon to create a well to put the salt in, being careful not to slice all the way through. (If you do, no big deal, many people preserve quartered lemons. It will work too). Add about 1 tablespoon of kosher salt to each lemon.
Place the lemons in the glass jar fitting them in as tightly packed as you can.
Close the jar and let them sit in a cool dry place for about a week. You'll notice juice beginning to accumulate in the jar.
After a week, open the jar, add your aromatics of choice - thyme, rosemary, peppercorns, coriander, cardamom, star anise, cinnamon, a whole pepper - your taste buds can be your guide. Then cover the lemons and aromatics with enough lemon juice to cover them all and close it up.
Let it sit out in that cool dry place for 3 or 4 more weeks. You can occasionally shake it about if you'd like. Right before you refrigerate, top with a seal of olive oil, then place in the refrigerator and start experimenting!