Thoroughly rinse and dry the lemons. Quarter each lemon, leaving about ¼ inch uncut so that one end of the lemon is still intact. Spread the lemon open and sprinkle salt (about 1 teaspoon or so) over the exposed flesh. Repeat until all of the lemons have been salted.
Place 1 tablespoon of salt in the bottom of the jar with a bay leaf, a couple of the juniper berries, and a couple of peppercorns. Press the lemons into the jar on top of the salt, smashing them in as tight as possible, and extracting any juice. Add the remaining bay leaves, juniper berries and peppercorns in as you go, or in any empty space that remains after the lemons are all in. Ensure that the lemons are completely covered in their juices, and/or adding more lemon juice if necessary. Seal and store in a warm place. Shake daily (or as often as you remember), to redistribute the salt. The lemons will be ready after 30 days. To use, rinse free of the salt and discard the interior pulp (If desired; when it comes to making the chicken mentioned in this post, I rinse the lemon, but leave the pulp in place.).
Notes
Feel free to play with any combination of spices you like here; cinnamon and clove are nice in place of the juniper berries and peppercorns!
Recipe by JJBegonia at https://jjbegonia.com/how-to-preserve-lemons/