I don't have a pattern, but if I were making castellating hose, I'd want 6 or 8 "castles" at the top of the sock, and would want them to be about an inch wide. Since I make my socks from the toe up, I'd work the sock until it reached the desired length, then knit an inch-wide section back and forth (in short rows) until it was about an inch long, then bind it off. I'd reattach the yarn to the live stitches, and bind off an inch-wide section, then work another 1X1" "castle", and bind it off, then reattach the yarn and so forth around the sock.
If your knitter makes her socks from the cuff down, she could make the "castles' on 3 separate DPNs, then join them together in the round using cast-on stitches between "castles", then make the sock according to her favorite method.

Clear as mud?