Stir bouillon into 1 cup of boiling water and stir to dissolve. Add pepper and poultry seasoning to liquid. Simmer chicken in broth and bouillon for about 30 minutes. Add celery, onion, and carrots. Continue to simmer until chicken and vegetables are cooked.
In a small bowl, mix together 1/4 cup corn starch and enough water to form a thin paste. Stir into cooking broth to thicken it into a light gravy. If you need like more thickening repeat with second 1/4 cup cornstarch. Bring up heat a bit so stew is bubbling lightly. Taste and add salt and pepper as necessary to your liking.