Place the pickling spice in the center of a piece of cheesecloth or coffee filter. Tie tightly with a long piece of string.
Place beef cubes, onion, carrot, crushed rosemary, garlic powder and bouillon cubes to slow cooker. Stir in tomatoes and wine. Add pickling spice bundle; cover.
Cook 8 hours on LOW or 4 hours on HIGH. Remove pickling spice bundle.
Thicken stew by mixing flour with 1 tablespoon water in medium bowl until smooth. Stir in several tablespoons hot liquid from stew, then stir flour mixture into stew. Cook and stir 2 to 3 minutes or until stew thickens slightly. To serve, place 1 slice bread in each bowl. Spoon stew over bread.