Slice the bread loaf horizontally and hollow out a little of the soft interior to make room for the filling.
In a bowl, combine the green olives, black olives, roasted red peppers, giardiniera, capers, garlic, olive oil, red wine vinegar, Italian seasoning, crushed red pepper flakes, and black pepper.
Mix well and let the olive salad sit for 10 minutes so the flavors blend.
Spread half of the olive salad evenly over the bottom half of the bread.
Layer the provolone cheese over the bread.
Add the salami, ham, mortadella, and pepperoni in even layers.
Top with the mozzarella cheese.
Sprinkle with grated Parmesan.
Add arugula or fresh basil if using.
Spread the remaining olive salad over the top half of the bread and place it over the sandwich.
Wrap the sandwich tightly in plastic wrap or foil.
Place a heavy skillet or baking sheet on top and refrigerate for at least 1 hour, preferably 4 to 8 hours.
Slice into wedges and serve.