Step 1Make an olive relish by combining the green and black olives with the pimentos, celery, cauliflower, carrot, garlic, parsley, oregano, vinegar and oil. Stir to blend, then set aside to marinate at least 2 hours, but preferably 4.
Step 2Slice the bread in half horizontally. Scoop out some of the bottom part, leaving a retaining wall on all sides. Drain the olive mixture, reserving the liquid. Spread half the relish onto the bread. Top with successive layers of lettuce, ham, mortadella, salami and cheese. Drizzle with a little of the reserved marinade. Spread the remaining olive relish over the layers. Top with the reserved half of the loaf.
Step 3Wrap the sandwich in plastic film. Place it on a baking sheet and weight it with something heavy such as an iron skillet or canned tomatoes. Refrigerate for at least 4 hours to compress. Cut into thin wedges to serve.