I worked out where I went wrong last night. The pattern said to pick up & knit 9 stitches, place marker, then knit 10. I had picked up one stitch per row, rather than spreading the 9 stitches across all the rows (about 20). So then the only thing that seemed to make sense was that knit 10 stiches meant pick up & knit 10 stitches. So I did. Continued knitting in the round, then had to pick up stitches on the other side of the heel flap before I'd got to it. Of course, what I should have done was spread the nine picked up stitches across the rows.
Is it just me, or could the pattern have been clearer? This is the first knit-in-the-round sock in a book of socks (the previous ones all had seams), so I assume it's aimed at first time sock knitters. OTOH, I haven't done any of the seamed socks or slippers - perhaps some of them had picked up stitches & were more specific about spreading them out, so the reader is assumed to already know about that.
Anyway, that was my first time picking up stitches along the side. Much easier than picking them up in the middle, which is what I've done before for
the teddies' arms.
Heading down to Carlow/Kilkenny today. I wonder if a moving car is a good place to frog a round...