Pat dry chicken with paper towels. Season with salt and pepper.
Heat oil in a large skillet over medium heat. Add chicken and cook for 4-5 minutes on each side. We are not fully cooking the chicken here. Rather, browning it a bit to build flavor. *
Meanwhile, place onion, celery, carrots, garlic, potatoes, thyme, rosemary, paprika, salt, and pepper into the crock pot.
Add the now-semi-cooked chicken thighs on top.
Pour the chicken stock and give it a stir.
Cook on low-heat setting for 5-6 hours or high-heat setting for 3-4 hours.
Place cornstarch in a small bowl and set it aside.
Thirty minutes before the end of cooking time, remove the chicken from the slow cooker and cut (or shred) into small pieces. Return it back to the crock pot.
Next, make the cornstarch slurry. Whisk cornstarch with 2-3 tablespoons of the liquid from the stew until it forms a paste. Stir it into the chicken stew.
Add the frozen peas, give it a big stir and continue to cook on HIGH until it is thickened to your liking. In my case, it took about 30 minutes.
Finish it off with lemon juice. Taste for seasoning and add more if necessary. Garnish with fresh parsley and serve.