Sardines are rare in most parts of the U.S. If you find yourself fortunate enough to come across freshly caught, glistening sardines, you have little choice but to buy as many as you can and preserve what you don't eat the same day. Sardines stay fresh only a few days, so you need to keep them on ice and cure them within 24 hours. Packing sardines in oil -- for best flavor, use quality extra-virgin olive oil -- after you cure them prevents oxygen from degrading their quality.
Scrape the scales off the sardine with the back of a knife; cut off the tail and fin with scissors. Cut the belly open from the tail to the head using scissors.
Hold the sardine belly under slow-running water and scrape out the guts from its tail to head with your finger. Rinse the sardine inside and out.
Make a vertical slice to the bones on each side of the sardine just behind the head. Hold the fish head and pinch both sides of the body behind the head; slide the body free from the head.
Open the body up like a book and remove the pin bones using tweezers.
Pour 1/4 inch of kosher salt in a shallow dish. Open the sardines and lay them flesh-side down in the salt. Cover the sardines with another 1/4-inch layer of salt.
Cover the dish with plastic wrap and place it in the refrigerator to cure for 3 hours. Rinse the salt from the sardines and transfer them to a food-storage container.
Cover the sardines with enough white vinegar or lemon juice to submerge them by about 1 inch. Cover the container and place it in the refrigerator to cure for 24 hours.
Pour about 1/4 inch of olive oil in another food-storage container and lay the sardines in it flesh-side down; you can stack the sardines. Sprinkle herbs and spices, such as thyme, sliced chilis and cloves, between the layers if desired.
Pour enough olive oil in the container to cover the sardines by 1/4 inch. Store the sardines, covered, in the refrigerator up to 1 month.
Lay the sardines flesh-side up in a shallow dish. Sprinkle equal parts of kosher salt and white sugar over the flesh until covered.
Drizzle equal parts of white vinegar, fresh orange juice and lemon juice over the sardines. Add fresh herbs, such as dill, thyme and white peppercorns, over the sardines.
Pour enough olive olive oil to cover the sardines by about 1/4 inch. Cover the dish with plastic wrap and place it in the refrigerator to cure for 24 hours.
Transfer the sardines to another food-storage container and cover with olive oil. Keep the sardines in the refrigerator, covered, up to 2 weeks.