Lay pork belly on cutting board and roll up lengthwise, with skin facing out.
Using butchers twine, tightly secure pork belly at 3/4-inch intervals.
Preheat oven to 275°F. Heat 1 cup water, soy sauce, sake, mirin, sugar, scallions, garlic, ginger, and shallot in a medium saucepan over high heat until boiling. Add pork belly (it won\'t be submerged). Cover with a lid left slightly ajar. Transfer to oven and cook, turning pork occasionally, until pork is fully tender and a cake tester or thin knife inserted into its center meets little resistance, 3 to 4 hours.Transfer contents to a sealed container and refrigerate until completely cool.
When ready to serve, remove pork belly and strain broth. Reserve broth for another use (like making ajitsuke tamago). Slice pork belly into thin rounds (it might help to cut it in half lengthwise first).
Reheat pork belly slices in soup broth with noodles and other garnishes. Alternatively, heat a small amount of reserved broth in a skillet and heat pork slices in broth until hot or reheat with a blowtorch, charring its surface. Serve.
View the recipe instructions at Serious Eats
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