Place your pork belly skin side down on a cutting board.
Roll up your pork belly tight. Using butcher’s twine, tie up the pork belly in the very center of the roll.
Tie up the pork belly every inch or so; at least 4 times on each side of the center tie.
Heat up the cooking oil in a Dutch oven over medium high heat. Brown the tied up pork belly on all sides for 10-12 minutes in total.
Mix together the sugar, soy sauce, mirin, and sake. Pour into the Dutch oven. Add in the ginger, garlic, and green onions. Bring to a boil uncovered.
Place a cover on the Dutch oven. Simmer for 90 minutes, turning every 20 minutes in the sauce.
Refuce the heat to medium low and continue simmering for 30 more minutes.
Take the pork belly out of the pot and let cool.
Strain the sauce of the ginger, garlic, and green onions.
Place the pork belly in a gallon sized storage bag with 1 cup of the strained sauce. Place in the refrigerator for 24 hours before use.
Save the rest of the sauce. This is now the tare sauce for the ramen.