Using a serrated knife, split the bread horizontally. Slather pesto sauce on one side and the tapenade on the other. Layer the meats, provolone, and basil leaves on the bottom half of the loaf. Scatter on the pepperoncini and red onion and lightly drizzle with olive oil. Season with black pepper.

Place the top half of the loaf on the sandwich. Heat a large griddle over medium heat (can be flat or ridged) and grease with olive oil. Place the sandwich on the griddle and press down with a heavy skillet or pan.

Cook until the bottom of the sandwich is crisp and golden brown, then flip and brown the top of the sandwich. Allow to cool to room temperature before slicing into individual servings with a serrated knife. Wrap each sandwich in foil for easy transport and serving.