In a medium bowl, combine the chopped green and black olives, capers, chopped garlic, parsley, and celery. Drizzle in the olive oil and red wine vinegar, then sprinkle with oregano, black pepper, and crushed red pepper flakes. Mix thoroughly and refrigerate overnight.

Slice the round Italian bread in half horizontally, gently scoop out some soft bread from the interior if preferred.

Spoon half of the prepared olive salad on the bottom half of the bread. Layer with mortadella, capicola, and Genoa salami, followed by slices of provolone and mozzarella cheese.

Spoon the remaining olive salad over the cheese layer and place the top half of the bread on top. Wrap tightly in plastic wrap.

Weigh down the wrapped sandwich with a heavy object and refrigerate for 1-2 hours or overnight.

For a warm sandwich, preheat oven to 350°F (175°C), wrap sandwich in foil, and heat for about 15 minutes.