Prepare your ingredients: dice the chicken, peel and dice carrots, slice the celery, and finely chop the onion and garlic. Set everything nearby for easy assembly.
Place the diced chicken in the bottom of the slow cooker. Scatter the carrots, celery, onion, and minced garlic over the chicken, creating a colorful base.
Pour in the chicken broth, covering the ingredients evenly. Add the rice, spreading it out gently over the top without stirring too much.
Drop in the bay leaf and sprinkle the thyme, along with a pinch of salt and pepper. Cover the slow cooker with its lid and set it to low for 6 hours.
As the soup cooks, you'll notice the broth bubbling gently and the aroma filling your kitchen with warm, savory scents. The chicken will become tender, and the rice will soak up the flavorful broth.
After 6 hours, open the lid carefully. Remove the bay leaf, and check that the chicken is shreddable and the rice is soft. If needed, cook for an additional 30 minutes.
Taste the soup and adjust the seasoning with more salt and pepper if necessary. For extra brightness, stir in chopped fresh herbs or a squeeze of lemon.
Let the soup sit for about 10 minutes with the lid slightly ajar, allowing flavors to meld. Ladle into bowls, making sure each serving has plenty of tender chicken, fluffy rice, and vegetables.