Step 1 Make the marinade by mixing the soy sauce, sugar and five-spice powder in a bowl until the sugar is completely dissolved. Stir in the sesame oil. Place the pork belly in a sealable plastic bag and pour the marinade over it. Marinate in the refrigerator for 4 hours, turning occasionally.
Step 2 Heat the oven to 450 degrees. Pierce holes every inch through the pork skin with a metal skewer. Place it skin side up on a rack set over a baking dish, containing about one-half inch of water. Roast until dark golden and crispy, about 1 hour, basting the top (skin) side with the soy sauce mixture every 15 minutes. Remove from the oven and let rest for 15 minutes before slicing. Thinly slice lengthwise with a serrated knife.