Mix the five-spice powder, brown sugar, sea salt, and paprika in a bowl to make the marinade. Rub this marinade on the pork skin, then wrap the sides with aluminum foil, leaving the skin exposed. Refrigerate overnight to let the fridge slightly dry out the skin's moisture, ensuring crispy pork skin when baked.

Next, use a small knife or needle to poke the pork skin with as many holes as possible. This helps achieve a crispy texture when baked.

Cover the pork skin with coarse salt to absorb moisture during baking, ensure even heat distribution, and add a bit of saltiness. Do not use regular table salt, as it will melt into the skin and become too salty. Place the pork belly in a preheated oven at 430°F (220°C) for 30 minutes. Remove, discard the coarse salt, and if there's too much rendered pork fat, pour it out. Return to the oven, lower the temperature to 390°F (200°C), and bake for another 20 minutes.

Take it out of the oven and tap the pork skin with a small knife to check if it's hard and crispy. If there are still soft spots, lower the oven to 350°F (180°C) and bake for another 10 minutes for this amount of pork belly.

Be careful when removing from the oven, as the baking tray will be very hot, and there will be a significant amount of rendered pork fat, almost a bowl's worth. You can save it for stir-frying or mixing with rice for added flavor. Once the pork belly has cooled slightly, slice and serve. Cut from the meat side, which is the bottom, as cutting directly from the skin side will result in a messy cut due to the crispy skin.