1. Place pancetta in a large skillet over medium-high heat; cook 4 minutes or until beginning to brown, stirring occasionally. Add sirloin; cook 3 minutes or until browned, stirring to crumble. Place sirloin mixture in a 6-quart electric slow cooker. Return skillet to medium-high heat. Add ground pork and sausage; cook 5 minutes or until browned, stirring to crumble. Add pork mixture to slow cooker.
2. Return skillet to medium-high heat. Add oil; swirl to coat. Add onion, carrot, and celery; sauté 4 minutes. Add tomato paste and garlic; cook 2 minutes, stirring frequently. Add wine; bring to a boil. Cook 2 minutes or until wine mostly evaporates, scraping pan to loosen browned bits. Add stock, tomatoes, 3/4 teaspoon salt, pepper, and bay leaf; bring to a boil. Carefully pour stock mixture into slow cooker; cover and cook on LOW for 6 hours. Discard bay leaf. Stir in remaining 1/4 teaspoon salt.