Brown the ground beef along with the onions and garlic in a large skillet over medium-high heat until fully cooked.
Place the cooked beef in the slow cooker and add the red wine, tomato paste, basil, oregano, parsley flakes, red pepper flakes, bouillon cubes, bay leaf, crushed tomatoes, salt, and pepper.
Cook on low for 6 hours, or on high for 3 hours. Serve over cooked spaghetti.