Step 1: Layer the chicken and vegetables - Start by placing the chicken thighs directly into the bottom of your slow cooker. Spread them out as evenly as you can. Add the sliced carrots, celery, and onion right on top. No need to be fancy here. This is rustic comfort food at its best.
Step 2: Mix the gravy base - In a small bowl, whisk together the chicken stock, au jus mix, chicken gravy mix, garlic powder, onion powder, and black pepper. Make sure everything is well combined so there are no dry pockets of seasoning.
Step 3: Pour and cover - Pour the gravy mixture evenly over the chicken and vegetables. Give it a gentle nudge with a spoon to make sure everything is lightly coated. Place the lid on the slow cooker.
Step 4: Slow cook to perfection - Cook on low for 6 hours or on high for 4 hours. The chicken should be tender and easy to break apart with a fork, and the vegetables should be soft but not mushy.
Step 5: Garnish and serve - If you like, sprinkle a little fresh parsley over the top before serving. Scoop into bowls, making sure everyone gets plenty of gravy, and enjoy while it is hot.