In a large skillet over medium heat, cook the 1 pound ground beef and1 pound Italian sausage until fully browned. Break it up as it cooks, and then drain off the grease.
Add the diced 1 medium onion to the skillet and cook for 3–4 minutes until soft. Stir in the 3 cloves garlic and cook 30 seconds more.
Transfer the meat mixture to your slow cooker. Add 28 ounces crushed tomatoes, 15 ounces tomato sauce, 2 tablespoons tomato paste,1 teaspoon dried basil, 1 teaspoon dried oregano, ½ teaspoon salt, ½ teaspoon black pepper, and ¼ teaspoon crushed red pepper flakes if you like a little kick. Stir well.
Cover and cook: LOW: 6–8 hours, or HIGH: 3–4 hours.
Give it a stir once or twice, during the cooking process.
If the sauce gets too thick, stir in ½ cup water or broth until it’s the texture you want. Taste and adjust seasoning.
Serve over pasta, spoon onto lasagna, pile onto subs, or freeze.