Use a block of pork belly. It's a bit different from the "three layer meat" (skin, fat, meat) they use in Okinawa, but it works well.
Cover the meat with salt, and rub it in well. I wrote down an amount of salt for the recipe, but basically you should pack the meat completely in salt.
Wrap the salted meat with newspaper. You can use paper towels too, but here we'll rely on the absorbent nature of newspaper.
Put the wrapped meat in a ziplock bag, eliminate the air from the bag and seal it up. Let it rest in the refrigerator for about 4 days.
Wash the pork well to remove the salt. Bring a pot of water with the green part of a leek and ginger to a boil, and put in the pork. Skim off any scum.
When you have removed the scum, boil the pork for about 1 hour. Use a big pot with plenty or water, or the water will boil off while you're cooking the pork.
Rinse the boiled pork again.
Slice about 6-7mm thick (like the pork slices on ramen noodles). Pan fry with a little oil over high heat until crispy.
Transfer to serving plates, sprinkle with some chopped green onion and enjoy!
Here is what I served when I made this recipe. Red beans and rice (osekihan), suuchikaa with cabbage and cucumber, green bean salad, and egg plant and aburaage miso soup.
Story Behind this Recipe
The "suukachidon rice bowl I had once was so delicious that I asked the restaurant staff how it was made. They explaind that "salt is rubbed in to pork and it's left for a few days and then fried up until crispy." Based on that short answer I did a lot of experimenting.
The key is to boil the pork in a lot of hot water in a large pot. If the water boils off it's not good. If you are cooking the pork when it's freshly boiled, use a non-stick frying pan and you won't need to add any oil.