Add all ingredients to a small bowl. Stir until well combined.
How to roast the pork belly in the oven:
Pat the pork belly dry using paper towels, then rub evenly with the seasoning on all sides. Transfer to an airtight container and refrigerate for 4 hours.
Very lightly oil a cast iron pan, then set the pan into the cold oven. Heat the oven to 450 degrees F. with the pan in it.
Once the oven has reached 450 degrees, set the pork belly into the hot pan using kitchen tongs. Roast, uncovered, for 15 minutes, turning every 5 minutes.
Reduce the oven temperature to 275 degrees F. Continue to roast the meat uncovered until tender, turning every 15 minutes. (This will take another 30 minutes to 1 hour, depending on the thickness of the piece.)
Transfer the roasted pork belly to a plate lined with a paper towel to soak up excess fat. Transfer to a cutting board and slice.