Combine the soy sauce, rice wine, oyster sauce, sugar, garlic, and oil; stir to combine.Dry the skin of the pork belly.
Add the pork belly to a baking dish or pan that can accommodate the pork and marinade. Pour marinade into the pan, making sure the level stays below the skin. Refrigerate for at least 4 hours or overnight.
Heat oven to 300F. Line a half sheet pan with foil and set a wire rack inside the pan.
Remove the pork from the marinade and dry the skin well if any moisture appears. Spread the cup of salt over the skin. Cook in the oven for 2 hours. Remove the salt crust and any salt that remains behind with a basting brush.
Increase the oven temperature to 450F. Return to the oven for 15-20 minutes, or until the skin is golden and crispy. Slice and serve.