Pour the chicken broth or water into the Instant Pot.
Arrange the frozen chicken breasts in the pot, leaving a little space between each piece when possible.
Season with salt, pepper, and minced garlic if using.
Lock the lid and set the pressure valve to Sealing.
Select Manual or Pressure Cook on High Pressure.
Cook according to the size of the chicken breasts (see the cooking time chart above).
Allow the pressure to release naturally before opening the lid.
Check that the thickest part of the chicken reaches 165°F (74°C).
Slice, cube, or shred the chicken as desired. For extra-moist shredded chicken, mix it with a little of the cooking liquid before serving.