Combine shank bone and water in a large stock pot; bring to a boil. Skim surface, and reduce heat. Cover and simmer 5 1/2 hours. Remove from heat. Cover and refrigerate overnight. Remove and discard excess fat. Strain broth through several layers of damp cheesecloth. Return broth to stock pot.
Bring broth to a boil; stir in remaining ingredients, except flour. Reduce heat; simmer, uncovered, 1 hour, stirring occasionally. Transfer 3/4 cup soup to a small bowl; add flour, stirring to make a paste. Add flour mixture to soup in stock pot; stir until well blended. Return soup to a boil; cook, stirring constantly, until soup is slightly thickened.
Ladle into individual soup bowls, and serve warm.