The Easy Chicken Stew I Make All Winter Long

Name: The Easy Chicken Stew I Make All Winter Long
Ingredients: 2 tablespoons neutral oil, like avocado or canola, divided; 2 pounds skin-on, bone-in chicken breasts (2 to 3 breasts); Kosher salt and freshly ground black pepper , to taste; 1 medium yellow onion , diced; 2 medium carrots , peeled and diced; 1/4 cup all-purpose flour; 2 teaspoons roasted chicken base or bouillon; 6 cups water , divided; 2 large stems fresh thyme or 1 teaspoon dried thyme leaves, optional; 1 pound sweet potatoes , cut into 1/2-inch pieces (about 3 1/2 cups )