In a medium saucepan, combine the chicken stock and water. Bring to a gentle simmer over medium heat. Add the boneless skinless chicken breast and cook for about 15-20 minutes or until cooked through. Remove the chicken and let cool.
In a mixing bowl, combine the Whole30 mayonnaise, fresh lemon juice, Dijon mustard, salt, and dried dill. Whisk together until smooth.
To the bowl with the dressing, add the shredded chicken, thinly sliced celery, and red seedless grapes. Gently fold everything together until evenly coated.
Cover the salad and let chill in the refrigerator for about 30 minutes before serving.
