Slow Cooker Beef Stew with Shiitake Mushrooms

1 medium onion, chopped (1/2 cup)

1 bag (8 oz) ready-to-eat baby-cut carrots

1 package (3.4 oz) fresh shiitake mushrooms, sliced

1 can (14 1/2 oz) Muir Glen® organic diced tomatoes, undrained

1 can (10 1/2 oz) condensed beef broth

1/2 cup Gold Medal® all-purpose flour

1 tablespoon Worcestershire sauce

1 teaspoon salt

1 teaspoon sugar

1 teaspoon dried marjoram leaves

1/4 teaspoon pepper

1 lb beef stew meat, cut into 1/2-inch pieces