Pat the chicken breasts dry with paper towels and trim any excess fat. Place them in the Instant Pot in a single layer.
Sprinkle the kosher salt, black pepper, garlic powder, and smoked paprika evenly over both sides of the chicken breasts, gently pressing the seasonings in for even coverage.
Pour the chicken stock into the Instant Pot around the sides of the chicken—not directly onto the chicken to avoid washing off the seasoning.
Secure the lid and set the valve to 'Sealing.' Select 'Manual' or 'Pressure Cook' on high for 10 minutes. When the cooking time is done, allow the pressure to release naturally for 5 minutes, then carefully perform a quick release for any remaining pressure.
Open the lid and let the chicken rest in the pot for 3-5 minutes before shredding for best results.
Use two forks to shred the chicken in the pot, or transfer the breasts to a cutting board for easier shredding. Return shredded chicken to the pot and toss with the juices to coat thoroughly.
Use immediately in your favorite recipes, or allow to cool before storing.