Occipital is the term usually used when referring to the base of the skull.

at the base of the skull

The mastoid process is located at the base of the skull and posterior to the ear.

The Sella turcica is found on the surface of the sphenoid bone, at the base of the skull. It's where we find the pituitary gland.

Chandranath Sen has written:

'Microsurgical Anatomy of the Skull Base' -- subject(s): Anatomy & histology, Atlases, Cavernous Sinus, Microsurgery, Skull, Skull base, Surgery