Spread the shredded lettuce in an even layer on a large cutting board.
Add the onion, pepperoncini, and tomato slices on top.
Layer the meats (salami, ham, pepperoni) over the veggies, then top with provolone slices.
Dollop the mayo, vinegar, Italian dressing, oregano, salt, and pepper directly onto the meat.
Using a sharp knife, chop everything together until you have a fine, creamy, evenly mixed filling (all pieces about the same size).
Divide the filling into 3–4 logs, each about the length of your hoagie buns. Place the open buns on top of the logs.
Slide a knife flat under each log, flip the bun over with the filling inside, and press gently to seal.
Serve immediately, or wrap in parchment for a portable lunchbox meal.