Heat olive oil in a large skillet over medium heat until shimmering. Add chopped onion and minced garlic, sauté for 2–3 minutes until fragrant and slightly softened.
Add ground beef to the skillet and cook, breaking it up with a spatula, until browned and no longer pink, about 8 minutes. Drain excess fat.
Stir in tomato sauce, tomato paste, oregano, salt, and black pepper. Simmer on low for 5 minutes until the sauce thickens slightly.
In a large mixing bowl, combine cottage cheese, half of the shredded mozzarella, and Parmesan. Stir until smooth and creamy.
Lightly grease the slow cooker with cooking spray. Spoon a thin layer of meat sauce on the bottom. Layer uncooked lasagna noodles over the sauce, breaking them to fit.
Spread half of the cheese mixture over the noodles, then spoon half of the remaining meat sauce on top. Repeat layers with remaining noodles, cheese, and meat sauce. Finish with remaining mozzarella on top.
Cover crockpot and cook on low for 4 hours, checking at the 3½-hour mark to ensure noodles are tender and sauce is bubbling around edges.
Turn off heat and let lasagna rest for 15–20 minutes before slicing. This helps layers set and prevents watery servings.
Garnish with fresh basil or parsley before serving if desired.
