1. Combine the olives, celery, gardiniera, roasted peppers, capers, olive oil and red wine vinegar in bowl. Season with salt and pepper and set aside.
2. Remove some of the soft bread center from each half of the bread. Spoon half of the olive mixture including some of the liquid onto the bottom half. Layer the salami, provolone, capicola and mortadella on top and finish with the remaining olive mixture.
3. Wrap the muffaletta with plastic wrap and weigh down with a cast iron pan for 1 hour before serving. The same techniques can be replicated by packing the muffaletta at the bottom of a picnic basket.