In a mixing bowl, combine the mayo, minced garlic, salt, and crushed red pepper flakes. Mix well to incorporate all the flavors. This spicy mayo will add a kick to your sandwich.
Slice the ciabatta bread diagonally into thick slices. Toast them in a toaster or oven until they are golden brown and crispy.
Spread a generous layer of the prepared spicy mayo on one side of each toasted ciabatta slice. Then, layer the roasted chicken slices, followed by the avocado slices, roasted red peppers, tomato halves, and arugula.
Finally, place the other half of the ciabatta on top to complete the sandwich. Cut it in half if desired, and serve immediately.