Cut beef into bite-size pieces; brown in oil in skillet. Transfer to a slow cooker. Cover with water; add tomato sauce and seasonings. Cover and cook on low for 8 hours, or on high for 4 hours, or until meat is tender. In a small bowl, combine flour and cold water to make a paste; stir into liquid in slow cooker. Cover and cook on high 30 minutes longer or until gravy is thickened. Serve over rice or potatoes.