The bake time for thin-sliced chicken breast should be around 15 minutes at 400 degrees. Thinner pieces will cook faster, which is why we actually recommend cutting thicker pieces in half before preparing baked chicken breast. We also recommend cooking your meat at a high temperature; at lower temperatures, thin pieces of chicken are more likely to dry out. Keep a close eye on your chicken to make sure that it doesn’t overcook. When it reaches an internal temperature of 165 degrees, it’s ready to eat.