Combine with oregano, basil, black pepper, and celery seed in a medium bowl. Add in olive oil, canola oil, and vinegar. Mix together and transfer the mixture into a glass jar (or other nonreactive container). Pour in more oil to cover if needed.

Cover jar or container and refrigerate at least 8 hours to overnight.

To make the sandwiches: Cut loaves of bread in half horizontally; hollow out some of the excess bread to make room for filling.

Spread each piece of bread with equal amounts of the olive salad, including oil.

Layer bottom half of each loaf with 1/2 of the salami, ham, mortadella, mozzarella, and Provolone slices.

Replace top half on each loaf and cut the sandwiches into quarters.

Serve immediately, or wrap tightly and refrigerate for a few hours; this will allow for the flavors to mingle and the olive salad to soak into the bread.