Linda's Picot Cast On
I use a waste yarn and cast on the
number of stitches (an even number) I want using one size larger needle than I
plan to use in the sock. I work at least two rows with the sock yarn and
the regular size needles. Then do a knit 2 together, yarn over row.
Then as many rows again as I did before the picot row. Then I remove the
waste yarn, fold the sock at the picot row and fuse the raw edge stitches with
the body of the sock.
You can do a knit 1, purl 1 rib or stockinette for the pattern at the top "hem". Any other rib looks odd to me. But, after the fusing you can change to another rib if you like, of course.
You can get the same look with using a waste yarn and casting on half the number of stitches you want. Then using the working yarn knit one, yarn over around, join into a circular piece, then knit the knitted stitches, purl the yarnovers. It isn't as neat or well defined as the first version but it works.