Cut the pork belly into square pieces, about 5 cm in size. Blanche the pork belly in boiling water for a few minutes to remove any impurities. Remove and set aside.

Heat the cooking oil in a large wok or deep pan over medium heat. Add the pork belly, skin side down, and cook until the skin is lightly browned and crispy. Flip the pork belly and cook for a few more minutes to brown the other side. Remove and set aside.

In the same wok or pan, add the light soy sauce, dark soy sauce, rice wine, sugar, water, ginger slices, and green onions. Stir to combine.

Place the pork belly back into the wok, skin side up, and bring the liquid to a boil. Reduce the heat to low, cover the wok with a lid, and let it simmer for about 90 minutes to 2 hours. This slow cooking process will make the pork belly tender and flavorful.

Occasionally check and stir the pork belly gently to ensure it cooks evenly and absorbs the sauce. If the liquid reduces too quickly, add a little more water.

Once the pork belly is fork-tender and the sauce has thickened, remove it from the wok and place it on a serving plate.

Optional: If you want a crispy texture, you can broil the pork belly in the oven for a few minutes until the skin becomes crispy. Be careful not to burn it.

Serve the Dongpo pork with steamed buns or rice. Spoon some of the sauce over the meat, and garnish with chopped green onions if desired.