Prepare your grill for 275 degrees F. You may add wood chips of choice, but honestly, it would be overkill to get this pork belly too smoky considering the scotch sauce.
If there is a large fat cap on the pork belly, trim it down a little. If it's ½" thick or so, leave it alone.
Combine the rub ingredients in a small bowl. Apply to both sides and edges of pork belly.
Place pork belly fat side down in the smoker, and let it go for 3 1/2-4 hours, depending on which unit you are using. Once the temperature reaches 180 degrees F. carefully remove the pork belly and wrap it in aluminum foil. Place it back into the smoker and let it go until the internal temperature reaches 200 degrees F.
To prepare sauce:
Add blood orange juice, regular orange juice, maple syrup, and bourbon to a saucepan.
Simmer over medium-high heat for 2 minutes, stirring often.
Add soy sauce, ketchup, and chili powder to the mixture, and reduce heat to medium.
Let the sauce simmer and thicken, stirring often. It will bubble up on the sides, that's fine; just keep an eye on it. Reduce heat to low if needed. The sauce should simmer for a good 5 minutes.
Next, stir in the 2 tablespoons of unsalted butter, remove the pot from heat and let the sauce stand for 5 minutes. The sauce should be a tad runny and syrup-like.
Remove pork belly from foil, and carefully place onto a cutting board. Using a sharp knife, cut pork belly into 1 1/4" cubes. Place cubes into the aluminum pan, and pour sauce over the top, making sure all pieces are well coated.
Cover the pan with foil, and place into the smoker for 30 minutes. Remove foil and cook for an additional 30-40 minutes until the sauce has reduced slightly and caramelized on the surface.