Remove root, tough outer leaves, and tops from leeks, leaving 2" of dark leaves. Slice leeks; rinse well, and drain.
Place ham bone in a 5-quart electric slow cooker. Add leeks and remaining ingredients. Cook, covered, on HIGH 1 hour; reduce heat to LOW, and cook 6 hours. Remove ham bone; cool slightly. Cut off meat and chop. Discard bone; return meat to stew.
Dutch Oven Method: Combine all ingredients in a large Dutch oven. Bring to a boil; cover, reduce heat, and simmer 1 1/2 hours. Remove ham bone, cut off meat, and continue as directed above.