Final answer:
The petrous ridge, part of the temporal bone, is the structure inside the skull that creates a distinctive slant by separating the middle and posterior cranial fossae.
Step-by-step explanation:
The structure inside the skull that forms a distinctive slant is known as the petrous ridge, which is part of the temporal bone. The petrous ridge separates the middle and posterior cranial fossae, playing a crucial role in dividing the interior space of the skull where the brain resides. The temporal bone contributes to the sides of the skull and houses the structures of the ear. The zygomatic arch is another notable structure that forms a bony arch on the side of the skull but does not create a slant like the petrous ridge. It is formed by the junction of the zygomatic process of the temporal bone and the temporal process of the zygomatic bone.