1. Prepare the Olive Salad:

• In a large bowl, combine the green olives, black olives, giardiniera, roasted red peppers, capers, celery, and garlic.
• Add the olive oil, red wine vinegar, oregano, and red pepper flakes. Season with freshly ground black pepper.
• Mix well to combine. Cover and refrigerate for at least 1 hour, preferably overnight, to allow the flavors to meld.

2. Assemble the Sandwich:

• Slice the round bread loaf in half horizontally. If the bread is very thick, remove some of the interior crumb to make room for the fillings.
• Evenly spread half of the prepared olive salad over the bottom half of the bread.
• Layer the mortadella, salami, capicola, provolone, and mozzarella over the olive salad.
• Spread the remaining half of the olive salad over the layered meats and cheeses.
• Place the top half of the bread loaf over the fillings. Press down gently but firmly to compact the sandwich.

3. Press and Serve:

• Wrap the assembled sandwich tightly in plastic wrap. Place the wrapped sandwich under a heavy skillet or pan and press it for at least 30 minutes.
• Unwrap the sandwich and use a sharp knife to cut it into wedges or slices. Serve immediately, or refrigerate for up to 24 hours.