First, thoroughly scrub each of the lemons to ensure they are entirely clean.
Slice off the tops & the bottoms of each lemon, leaving just the main belly of the fruit intact.
Cut each lemon into quarters, but be sure to leave the ends attached – slice just ¾ of the way into each lemon.
Sprinkle one teaspoon of salt across the bottom of your chosen jar.Pour another teaspoon of salt into the cuts of each lemon, being careful not to lose too much.
One by one, place the lemons – cut side down – into the salted jar. Between each lemon layer, sprinkle another teaspoon of salt. Use a muddler of sorts to press down hard on each lemon, to ensure it releases its juices. Repeat until all of the lemons are packed into the jar, and sprinkle a final layer of salt on the very top.
The lemon juice should be at least halfway up the jar by this point, if not you need to press harder on the lemons. Once past the halfway mark, fill the remaining space in the jar with the sterile water; pouring up to the very rim of the jar. Seal the jar tightly.
Leave the jar out at room temperature for 3 days – shaking vigorously every now and then – and then move to the fridge for a further 3 weeks, taking the jar out for a good shake whenever you think of it.