To make the dressing. Combine all ingredients in a glass jar and whisk until smooth. Taste and adjust the salt and chili flakes Preheat the grill or grill pan to high. Rub each half of the bread with some dressing. Grill the bread, cut side down, for 3-5 minutes or until grill marks appear. Spread the pesto over the bottom piece of bread. In the following order, layer the pepperoncini, basil, parmesan, and sliced peppers. Drizzle with the dressing. Layer the prosciutto, salami, pepperoni, and cheese slices. Add the arugula and toss with the dressing. Add the top piece of ciabatta. Push down on the sandwich. Cut into 6 sandwiches. You can also wrap the uncut sandwich tightly and place it in the fridge for up to 1 day before serving.