Preheat the slow cooker on high for 20 minutes. Spray the insert with nonstick cooking spray.
On a clean surface, stretch, roll and form the dough into roughly the same shape as the slow cooker insert. The goal is a nice, thin crust. Place in the cooker and spread out if necessary. Cook on high, UNCOVERED, for 1 hour without toppings.
Shingle the mozzarella slices over the dough and up the sides about 1 inch above the crust. Overlap each slice, moving in a clockwise circle until the perimeter is covered. Place 1 more slice to cover the empty spot in the middle, if necessary. Shingle a layer of pepperoni the same way you did the cheese. Follow with a small layer of the pizza sauce. Sprinkle with the Parmesan.
Cook on high until the cheesy crust is dark and caramelized and the bottom is firm and brown, another hour. Carefully take out of the slow cooker using a spatula. Garnish with the basil and crushed red pepper.
This recipe was developed using a 6-quart slow cooker, if yours is a different size, decrease the amount of dough if necessary so you have a fairly thin layer. Regardless of the cooker size, make sure the dough is mostly cooked through before adding the toppings. The middle should be slightly firm to the touch.