Doublemassa from Hats On

I would like to knit the Doublemassa from Hats On. It calls for fingerling weight yarn, then start with the liner, casting on 12 stitches on a circular needle, joining and begin knitting. Am I missing something, how do you cast on 12 stitches on circular needles and are able to join them? Also at 6 1/2 stitches = inch, wouldn’t you have to use at least sport weight or worsted weight yarn? Any insight is appreciated! Knitting Grammy

Uhh… that doesn’t sound right, but I looked it up on Ravelry and that’s what it says about the yarn and gauge. :??

You can’t cast on 12 on a 16" circular needle…you’d have to use two circs or magic loop, or use DPN. However, casting on 12 in fingering weight wouldn’t be enough for a hat for a human. Something’s not making sense to me. I hope someone else has this book to help you out.