Slice the round loaf of bread in half horizontally.
Hollow out some of the bread from both halves to create space for the fillings.
Prepare the olive salad by mixing chopped olives, celery, garlic, and olive oil in a bowl.
Layer the bottom half of the bread with sliced mortadella.
Add a layer of salami on top of the mortadella.
Place slices of provolone cheese over the salami.
Spread a generous portion of the olive salad on top of the cheese.
Add layers of ham and then more cheese if desired.
Close the sandwich with the top half of the bread.
Wrap the sandwich tightly in plastic wrap and refrigerate for at least an hour to meld the flavors.