Brine the lemons at least a month before using. Store-bought preserved lemons are a fine substitute and are available online or at specialty-food stores.
Cut a 3-inch-long, 1/2-inch-deep slit around the equator of each lemon. Pack 1 to 2 teaspoons salt into each slit. Pour 1/2 of the remaining salt into an airtight glass jar that fits the lemons snugly.
Pack lemons in jar. Pour lemon juice and the remaining salt over lemons. (The jar should be full.)
Cover, and refrigerate for at least 1 month or up to 2 months.