Preheat the oven to 350 degrees F and put a large pot of salted water on to boil.
Add the lasagna noodles to the boiling water and cook to al dente, according to the package directions. Drain the noodles, toss with a small amount of olive oil and spread them flat on 2 sheet pans to cool.
Meanwhile, in a large 3-quart skillet, heat 2 tablespoons olive oil over medium heat.
Add the sausage and cook, stirring occasionally and breaking up the meat with a wooden spoon, until no pink is left, about 12 minutes. Set aside to cool.
In another large skillet over medium heat, add the ground beef and cook, stirring occasionally and breaking up the meat with a wooden spoon, until browned and crumbled, about 15 minutes. Drain off and discard any fat.
In a medium saucepan, heat the remaining 2 tablespoons olive oil over medium heat. Add the onion and garlic and cook until browned and the onions are soft, 6 to 8 minutes. Add 2 jars of tomato sauce, the onion and garlic powders, seasoned salt and salt and pepper to taste. Bring the sauce to a boil, lower the heat to a simmer and cook, uncovered, over medium-low heat, for 10 to 15 minutes. Add the beef to the sauce, stir together and set aside.
Assemble the lasagna: Spread half of the beef and sauce mixture in the bottom of the baking pan followed by half of the ricotta cheese in a thin layer. Add half the sausage chunks, then 2 cups shredded mozzarella and a layer of noodles, overlapping them slightly. Repeat layering the same order once more. Top with the remaining jar of tomato sauce, then top completely with the thin slices of mozzarella.
Bake the lasagna until the sauce is bubbling and the cheese is browned, 40 to 45 minutes.