To a large slow cooker add in the chicken broth, chicken, minced garlic, and seasonings. Place the lid on top. Cook on low for 6 hours or until the chicken is cooked through.
Once the time is almost up, bring a large pot of water to a boil and add the pasta in. Cook the pasta according to the package instructions. Drain and set to the side.
Remove the chicken from the slow cooker and shred it with two forks or chop it into smaller pieces. Add the chicken back into the slow cooker.
Add the water and cornstarch to a small bowl whisk to combine.
Add the cornstarch slurry, heavy cream, cooked pasta, and spinach into the slow cooker stir well. Let cook for an additional 10 minutes.