1Place pork chops in 3 1/2- to 4-quart slow cooker. Top each chop with onion slice and sprinkle with garlic. Pour barbecue sauce over chops.
2Cover and cook on low heat setting 5 to 6 hours.
3About 5 minutes before serving, remove pork from cooker; place on serving platter and cover to keep warm.
4Mix water and cornstarch in 2-cup glass measuring cup or small microwavable bowl until smooth. Pour 1 cup of the juices from cooker into cornstarch mixture; mix well. Microwave uncovered on High 1 to 2 minutes, stirring once halfway through cooking, until mixture boils and thickens slightly. Serve sauce with pork.