In a large skillet, heat the oil over medium-high heat. Season the chicken with salt and pepper and brown on both sides; place them into slow cooker pot. Toast up the pasta in the same skillet the chicken was browned up in. Add the carrots, celery and water to the slow cooker, cover and cook undisturbed for 4 hours on high or 6-8 hours on low.
Add pasta to the soup 15 minutes before serving. Once the soup is done cooking, liven it up with freshly squeezed lemon juice and a bit of zest!