Season ribs with salt and pepper. Heat a non-stick skillet over medium-high heat. Brown ribs on all sides, working in batches. Do not overcrowd the pan. Transfer ribs to slow cooker as they are browned. Discard any fat that renders from the meat.
In a medium bowl, mix together the ketchup, chili sauce, brown sugar, vinegar, oregano, garlic powder, thyme, bay leaf, Worcestershire sauce, tomato paste, hot sauce, and salt and pepper.
Pour sauce over ribs in slow cooker, and turn to coat. Cover, and cook on Low 6 to 8 hours, or until ribs are tender. Remove bay leaf and discard before serving.