Make the dressing: In a small jar, combine olive oil, red wine vinegar, Dijon, garlic, oregano, salt, pepper, and red pepper flakes.
Seal and shake until emulsified. Taste and adjust salt or vinegar as needed.
Prep the greens: Rinse and dry the romaine and spinach well. Chop into bite-size pieces and place in a large bowl.
Chop the mix-ins: Slice the salami and prosciutto, cube the provolone, halve the olives and tomatoes, slice the red onion and pepperoncini, and drain the artichokes and roasted peppers.
Layer the salad: Add meats, cheeses, olives, artichokes, peppers, tomatoes (if using), onion, and herbs on top of the greens.
Toss with dressing: Pour about two-thirds of the dressing over the salad.
Toss gently until everything is lightly coated. Add more dressing if needed.
Taste and finish: Adjust seasoning with a pinch more salt, a squeeze of lemon, or extra herbs if you like. Serve right away.