Make the garlic paste: In a medium bowl, combine the garlic, rosemary, salt, black pepper, and red pepper flakes.

Make the porchetta: Place the pork belly skin-side up on a clean surface and score the skin in a cross-hatch pattern. Flip the belly over and season the flesh side with salt, black pepper, and half of the garlic paste.

Place trimmed pork loin in the center of the belly and rub with the remaining garlic paste. Season with salt and black pepper. Roll the pork belly around the loin to form a cylindrical shape and tie tightly with butcher's twine at 1-inch intervals. Season the outside with salt and black pepper, then place on a rimmed baking sheet. Transfer to refrigerator, uncovered, and let air-dry overnight.

When ready to cook, set the Traeger temperature to 180℉ and preheat with the lid closed for 15 minutes. For optimal flavor, use Super Smoke, if available.

Place the porchetta directly on the grill grates, seam-side down. Insert the probe into the center of the roll. Close the lid and smoke for 1 hour.

Increase the Traeger temperature to 325℉ and continue roasting until the internal temperature reaches 135℉, about 2 ½ hours. If the exterior begins to burn before the desired internal temperature is reached, tent with foil.

Remove the porchetta from the grill and let rest 30 minutes before carving crosswise into 1-inch-thick slices. Enjoy!