In a small bowl, stir together the mayonnaise, Dijon mustard, and 1 tablespoon of pepperoncini brine until smooth. This gives you a tangy, slightly spicy spread that cuts through the rich salami.

Toss the arugula with the olive oil and a pinch of black pepper in a separate bowl. This prevents the greens from tasting dry against the meat and cheese.

Spread the mustard-mayo mixture on both cut sides of the ciabatta. On the bottom half, layer half the provolone, then all the salami, folding each slice slightly so it creates texture rather than lying flat.

Scatter the pepperoncini rings and roasted red peppers over the salami. Top with the remaining provolone, then the dressed arugula. Close with the top half of the bread and press down firmly.

Cut each sandwich in half with a serrated knife using a gentle sawing motion to avoid squishing the bread. Serve immediately, or wrap tightly in parchment paper for up to 2 hours.