Add the remaining 1 tablespoon oil to the pan. Add carrots, celery, onion, thyme and the remaining 1/4 teaspoon pepper; cook, stirring occasionally, until the vegetables are crisp-tender, 5 to 7 minutes. Sprinkle the reserved flour over the vegetables; stir to coat. Stir in broth and the chicken. Cook, stirring occasionally, until the stew is thickened, about 3 minutes. Add the gnocchi and peas and cook, gently stirring, until the gnocchi are hot, about 2 minutes.