Or bind off at the beginning, then knit to the end of the row and then turn and bind off at the beginning of the purl row?
Yup, that's right, you can only BO at the beginning of a row.
That's why it says: Bind off 9 sts beg of next 2 rows. 64 sts.
Isn't learning to read knitting fun? LOL
You can't knit the left sock first. Ever.