okay, here's my attempt at explaining the double-knit tubes technique i used to make the kodama dolls.
basically, what you do is cast on an even number of stitches, in this case 6.
carefully slip it off your needle,
fold it in half,
and then slide it back on to your needle, alternating stitches from each half. so, your original six stitches get picked up in this order: st 1, st 6, st 2, st 5, st 3, st 4.
to make the kodama dolls, you start by knitting both legs at once, each with a separate ball of yarn. so, repeat the steps above so that you have two sets of stitches - one for each leg.
now, the tricky part.
when you start knitting, you keep the two halves separate by knitting one stitch, bringing the yarn to front,
slipping one purlwise,
bringing the yarn to the back,
knitting one stitch,
bringing the yarn to front, slipping one purlwise, bringing the yarn to the back. keeping the above example, you’d knit st 1, slip st 6, knit st 2, slip st 5, knit st 3, slip st 4, then turn, and knit st 4, slip st 3, knit st 5, slip st 2, knit st 6, and slip st 1. it takes a bit of practice to keep the two halves separate – it’s easy to get the stitches caught around one another – so take it slow.
once you've done a few rows, it's a little clearer to see how what you're knitting looks like a tube - whether you look at it from front or back, it will look like a strip of stockinette three stitches wide, even though you have six stitches on the needle.
and this is important to remember – you're only knitting half a row at a time! what feels like knitting two rows is actually only knitting one row, since you’re only working half the stitches. so when you’re knitting this pattern, remember this if you’re counting rows as you knit them – and count the rows up from the bottom to double-check your progress.
there’s a really great description of how to use double-knitting to knit two socks at once at knitty. it also has better pictures - not blurry like mine!