Preheat the Traeger grill to 450°F (232°C). Set a wire rack over a sheet tray.

Toast the fennel seeds until fragrant, about 1 to 2 minutes.

Crush the toasted fennel seeds with the mortar and pestle.

Combine the crushed fennel, rosemary, thyme, dark brown sugar, 1/2 teaspoon chili flakes, and 1 teaspoon sea salt in a mixing bowl.

Rub the pork shoulder with 2 tablespoons olive oil. Coat it evenly with the prepared spice rub.

Insert the meat thermometer probe into the center of the pork. Let the pork stand at room temperature for 60 minutes.

Place the pork on the rack in the grill. Roast at 450°F (232°C) for 20 minutes.

Reduce the grill temperature to 300°F (149°C). Roast the pork until it reaches 165°F (74°C) internally, about 120 minutes.

Wrap the cooked pork in aluminum foil. Rest it for 20 minutes.

Slice the rested pork into thin strips. Sprinkle the sliced pork with sea salt.

Combine mayo, minced 2 garlic cloves, pepperoncini peppers, pepperoncini brine, and sea salt in a bowl.

Mix the pepperoncini mayo until smooth. Set it aside for sandwich assembly.

Heat a skillet over medium heat. Add 2 tablespoons olive oil, the remaining 1/2 teaspoon chili flakes, and sliced 5 garlic cloves.

Cook the garlic and chili flakes for 1 minute. Add the broccoli rabe and a pinch of sea salt.

Sauté the broccoli rabe until softened, about 4 minutes. Stir in the fresh lemon juice.

Split the sub-style rolls and drizzle their cut sides with the remaining 1 tablespoon olive oil.

Place 2 provolone cheese slices in each roll. Broil until the cheese is melted, about 2 to 3 minutes.

Spread about 2 tablespoons pepperoncini mayo inside each toasted roll. Add an equal portion of sliced pork.

Top each sandwich with an equal portion of broccoli rabe. Serve immediately while the cheese is melted.