Cut the chicken into 1-inch squares and place on a cutting board.
Season the diced chicken evenly with salt, black pepper, garlic powder, onion powder, and paprika (if using); set aside.
Heat 1 tablespoon oil in a large skillet over medium to medium-high heat until shimmering and a drop of water sizzles on contact.
Add the chicken pieces in a single layer without crowding; leave space between pieces. Work in batches if necessary.
Cook until the pieces brown on the first side, about 2–3 minutes, then flip and brown the other side for another 2–3 minutes.
If pieces are not cooking quickly, add 1–2 teaspoons of chicken stock to the hot skillet and immediately cover to steam for a short time; continue until the internal temperature reaches 165°F (74°C).
Remove the chicken when fully cooked (no pink inside) and repeat with any reserved batches.