Slice the Italian loaf in half lengthwise and scoop out a bit of the bread if needed.
In a mixing bowl, whisk together mayo, red wine vinegar, garlic, oregano, chili flakes, salt, pepper, pepperoncini, and red onion.
Add shredded iceberg lettuce and toss until fully coated.
On the bottom half of the loaf, layer provolone, ham, soppressata, salami, and pepperoni.
Add tomato slices, a drizzle of olive oil, and a sprinkle of salt, pepper, and Parmigiano-Reggiano.
Top with the dressed grinder salad.
Close the sandwich firmly.
Optional: Toast the sandwich at 375°F for 3–5 minutes until warmed and slightly crisp.