Prepare a large 13" baking dish, I used a cast iron skillet. Brush olive oil on bottom and sides to coat. Do not over grease, this dish has enough fat in it!!!
Cook the Italian sausage till just done, don't overcook.
Wash potatoes, then slice thinly, I use a mandolin on medium cut. If using the large round deli sliced hard salami and pepperoni, cut slices in half. If using the smaller round of each you may need a pound of each one.
Layer potatoes with salami and pepperoni halves, then spoon on the Italian sausage. Sprinkle with Italian seasoning, granulated garlic and black pepper. I would advise against using salt, this dish is already pretty salty from the meats used.
Cover tightly with foil, place in a preheated 350º oven for 30 min. Remove foil and bake another 30 min.
Remove from oven, turn broiler on low. Spoon on pizza sauce (drizzle), not to completely cover the dish, just hit and miss. Then sprinkle on cheeses and red pepper flake. Return to oven under a low broiler for about 5 min, just until cheese is melted and slightly brown. Remove and allow to cool for a few minutes, if you can wait that long, enjoy!!!