Stir together sun-dried tomato pesto and mayonnaise. Spread over ciabatta halves.
Top bottom half of loaf with salami, mortadella, roasted red peppers, provolone, basil, arugula and pepper. Cap with top half of loaf.
Wrap loaf in plastic wrap. Refrigerate on baking sheet and weigh down with cast-iron skillet or heavy pan for at least 1 hour or up to 8 hours. Cut sandwich into 8 pieces. To serve, secure each piece with toothpick.
Substitute fontina cheese for provolone cheese.
If desired, spread sandwiches with basil pesto or olive tapenade instead of sun-dried tomato pesto.