I'll add one more tip on these socks. This one is not errata, just a design choice.
When beginning the heel flap and when beginning the toe you are switching from the pattern to regular knitting. The pattern has yarnovers so when you begin the heel flap or toe you will have holes on the first row due to the yarnovers from the last pattern row. You can actually see the holes in the photo in the book.
If you want to avoid those yarnover holes on the first row of the heel flap and the first row of the stockinette toe: when you get to the yarnover from the last pattern rowknit the yarnover through the back loop to close it up.