Place the chicken tenders in a large pot and pour in the low-sodium chicken stock so the chicken is mostly submerged.
Bring the stock to a gentle simmer over medium heat and poach the chicken for about 15 to 20 minutes, or until the internal temperature reaches 165°F and the chicken is cooked through.
Remove the chicken from the stock and let it cool slightly, then shred finely using a stand mixer with the paddle attachment or by pulling apart with two forks.
Pat the shredded chicken dry with paper towels if needed to avoid a watery salad.
In a medium bowl, combine the mayonnaise, finely minced celery, dry Ranch dressing mix, salt, and ground black pepper; stir until well blended.
Add the shredded chicken to the dressing mixture and mix thoroughly until the chicken is evenly coated.
Transfer the chicken salad to an airtight container and chill for a couple of hours to let the flavors meld before serving.
Serve the chicken salad in sandwiches or on a bed of lettuce as desired.