1. Trim any excess fat off the roast. Season both sides with salt and pepper and place in a slow cooker.
2. In a medium bowl, combine onion with fresh or frozen and dried cranberries, ginger, ketchup, brown sugar, mustard powder, and vinegar. Stir well to combine. Pour cranberry mixture over roast. Turn roast over once or twice to coat it on all sides with the sauce.
3. Cover slow cooker and cook the roast on low heat for 8 to 9 hours (depending on the size of the roast), until meat is tender.
4. When meat is cooked, remove it from the slow cooker and set it aside to rest on a cutting board. Set slow cooker to high heat. In a small bowl, combine flour and water, stirring until smooth. Pour flour mixture into sauce in the slow cooker, stir well, cover, and let mixture simmer, stirring occasionally, for about 10 minutes, until slightly thickened.
5. Slice meat across the grain into thin slices and transfer to a platter. Ladle the sauce over each slice. Serve hot.
Source: Hannaford fresh Magazine, November - December 2010