1. Bring 3 quarts water and ham bone to a boil in a large stock pot. Boil until meat from the bone comes off easily, about 1 hour. Remove bone from broth. Allow bone to cool enough to touch; remove as much meat as possible. Transfer meat to a resealable plastic bad, seal, and refrigerate. 2. Pour broth into a large bowl, cover, and refrigerate overnight. Skim and discard any fat from the top of the chilled broth; transfer broth to a large pot. 3. Bring broth to a boil; add potatoes, cabbage, celery, and reserved ham. Continue to simmer until potatoes are tender, about 45 minutes. 4. Whisk 1/2 cup water and flour in a bowl; whisk into potato-ham soup until thickened. Add light cream, stir.