Cut the carrots, celery, and potatoes into ½ inch bite sized chunks, add to a bowl, then set aside.
Cut chicken thighs into 1 inch bite sized chunks, and season with salt and pepper. Add the seasoned chicken thigh pieces to a large skillet set over medium-high heat and cook until the pieces have browned all over. Kill the heat, remove the chicken pieces to a bowl and set aside.
In a large stock pot or Dutch oven over medium heat, then add the oil. Once oil is heated and is lightly smoking, add the carrots, potatoes, and celery. Season lightly with salt and pepper, then cook for 10 minutes or until the veggies start to soften. Add the garlic, ginger and browned chicken pieces to the pot and mix to combine.
Pour the stew base over the meat and vegetables then mix to coat everything in the mixture. Pour in the chicken stock and mix once more. Cover the pot and reduce the heat to medium low. Simmer with the lid on for 20 minutes.
Remove the lid, stir the stew and taste. Adjust seasoning with salt and black pepper, then add the cornstarch slurry and mix to thicken the stew.
Serve by evenly portioning out the stew and rice side by side in bowls, and garnish with furikake seasoning or thinly sliced green onion if desired.