In a large pot, bring 5-6 cups of water to a rolling boil. Add diced carrots, sliced celery, chicken bouillon cube, and a pinch of salt. Simmer for 5-10 minutes until vegetables soften.

Add diced cooked chicken meat and long grain rice. If available, include leftover chicken skin and fat for extra flavor. Cook until rice is tender and plumped, about 15-20 minutes.

Slowly stir in cornstarch or flour while whisking to avoid clumping, until the soup thickens to a silky consistency.

Season with salt and black pepper to taste. Adjust consistency by adding more water for thinner soup or more rice for thickness. Optionally add extra bouillon for more flavor. Ladle into bowls and serve hot.