To avoid that little gap, hole, or loose stitch at the top of the heel flap when picking up the gusset stitches:
WOW. Why did I never think of this? In case that link breaks — all you do is, while picking up stitches along the edge of the heel flap, pick up one more along the same column after you reach the top (bottom?) of the heel flap. On the other side of the heel flap, just start picking up stitches one stitch below the corner where the flap meets the leg, in the same column that becomes the edge of the heel flap. (It takes a lot of words to describe this trick, but just try it; it’s as simple as can be.)
Presto. No gap, no hole, no need to twist anything.
More details about these socks on Ravelry: http://ravel.me/kayray/lps
Look, no gaps, no holes: