Gather all your equipment and ingredients. Start by shredding any leftover roast chicken into bite-sized pieces, setting aside.
Peel and dice the carrots and celery into small, even pieces. Finely chop the onion and mince the garlic cloves. These veggies will add flavor, texture, and color to your soup.
Add the shredded chicken, chopped veggies, chicken broth, dried thyme, bay leaves, and a pinch of salt and pepper into the crockpot. Stir everything together until combined, and the ingredients are evenly distributed.
Cover the crockpot and cook on low for about 6 hours. As it cooks, you'll notice the house filling with a savory aroma, and the veggies will soften, turning tender and fragrant.
Halfway through, check the broth and give it a gentle stir if needed. Taste and adjust the seasoning with more salt, pepper, or a splash of lemon juice for brightness.
Once the cooking time is up, remove the bay leaves and test the veggies—they should be soft, and the chicken tender and shreddable. If you're adding noodles or rice, stir in the cooked grains now and cook on high for an additional 20 minutes until heated through.
Taste the soup one last time, adjusting the seasoning and adding a squeeze of lemon juice if desired. Let the soup sit uncovered for a few minutes to settle and deepen in flavor.
Spoon the warm, hearty soup into bowls, garnish with fresh herbs if you like, and enjoy this comforting, rustic dish with crusty bread on the side.