Season chicken thighs with 1 ½ teaspoons of salt and a little bit of pepper. For extra flavor, heat a large skillet to a medium heat. Add butter. Once the butter melts, sear chicken thighs until golden brown, about 3-4 minutes per side.
Transfer chicken to the slow cooker along with any accumulated juices. Cover with onion, carrots, celery, garlic, thyme and remaining salt. Pour all but ½ cup of chicken stock on top. Reserve the ½ cup chicken stock for later.
Turn the slow cooker on low and cook for 5-6 hours or until chicken is cooked through.
Remove chicken thighs from the slow cooker. Season broth to taste with salt and pepper. Whisk remaining ½ cup chicken stock with flour. Stir in to the broth. Stir in egg noodles. Cover and turn the slow cooker back on to high and cook another 1-2 hours or until noodles are cooked through.
While the noodles, cook, shred chicken with two forks.
Remove thyme sticks from the noodles and broth. Stir chicken along with any accumulated juices back to the slow cooker. Season to taste with salt and pepper. Add more chicken broth if desired.
You don't have to, but I do like to sear the chicken in a skillet before adding them to the Crockpot. It adds more flavor, but it will still be yummy without doing this.
Feel free to add in other veggies. Mushrooms and bell peppers are great additions