Heat the oven to 350 F/180 C. Place a rack on a baking sheet.
With a sharp knife, make several parallel cuts across the skin of the pork belly, about 1/4-inch apart. Cut through the skin and fat but not into the meat.
Sprinkle the pork all over with kosher salt and freshly ground black pepper. Drizzle with olive oil and rub it all into the pork.
Place the pork on the rack, skin-side up.
Roast for 2 to 2 1/2 hours or until the meat is very tender and falling apart. Increase the heat to 425 F and roast for about 20 minutes longer to crisp the skin even more.
Remove the pork from the oven and let rest for 10 minutes before slicing.
Slice thinly, using the cuts in the skin as guides.
