Start by chopping the vegetables and cutting the potatoes into even pieces. This helps everything cook evenly in the slow cooker. If you are using chicken breasts, you can leave them whole for easy shredding later.
Place the chicken, carrots, celery, onion, potatoes, garlic, broth, tomato paste, thyme, parsley, bay leaf, salt, and pepper into the slow cooker. Stir gently so the tomato paste blends into the broth.
Cover and cook on low for 6 to 7 hours or on high for 3 to 4 hours. The chicken should be tender and the potatoes should be soft when done.
Remove the chicken and shred it with two forks, then return it to the crockpot. This gives the stew a hearty, comforting texture.
For a thicker stew, stir flour with a little broth from the pot or mix cornstarch with water, then add it back in. Cook for another 15 to 20 minutes until slightly thickened.
Remove the bay leaf, taste the stew, and adjust the seasoning if needed. Serve warm in bowls and enjoy every cozy spoonful.