Left side of a-shaped over apron?

[eahuntley]

I'm not fully understanding what's going on on the left side of the over apron. Where do I sew to secure that edge? The X-kilt manual(2nd edition, written by Alan Hebert) says something about folding the raw edge under, but I'm pretty sure there isn't a raw edge on the left hand side. I consider a raw edge to be an edge that has an unhemmed cut in it. Maybe I'm misunderstanding?

And another question: is a-shaping always done, or are there times when you would choose to have a squared off over apron?