The slab is the one that's less-than-vertical: it slopes away from you. The opposite of the overhangs, which are the ones that, er, hang over you.

Yay for V1s! Yay for your foot not falling off! Though it is vitally important to have one's excuses ready to hand, and nodding sagely and referring vaguely to an injury is always a good one ...

(Btw, I don't know if you have any interest at all in yoga, but since you're in that general area, I thought I'd mention I found out that there's a yoga studio just down the street from the Arch.)