Combine chicken, water, onion, salt, pepper, oregano, and sage in a large Dutch oven; bring to a boil. Reduce heat; cover and simmer 2 1/2 hours or until chicken is tender. Remove chicken from broth; cool. Bone chicken, and cut meat into bite-size pieces; discard bones, and set meat aside.
Add chicken, corn, potatoes, celery, and carrots to broth; simmer, uncovered, 1 1/2 hours or until vegetables are tender.
Combine flour and water, stirring until smooth. Add flour mixture to stew; cook, stirring frequently, until stew is thickened. Serve immediately in individual bowls.