In reply to Greasy Prusiks:
Some conflation here of framing and angle-of-view.
As mentioned above, using a wideangle lens and pointing it up will make the slab appear slabbier due to keystoning, giving you the 'shallow walks' issue. So avoid this. Shooting from the side is generally better. Shooting down tends to remove any visual clues to the angle, although again a very wide lens may make it appear slabbier.
Framing the shot relatively wide (doesn't mean a wide lens necessarily, just back up) allows you to include context, and particularly the horizon, which gives viewers a reference for the angle of the rock.