Or start with any cast on.
cast on an even number of stitches.
divide the stitches evenly (a DPN really helps -or one of those clover stitch holder that is double ended)
fold the knitting in half (cast on row)
hold the two needle as you would for a 3 needle bind off.
take yarn and *knit 1 from front needle.
bring yarn forward (as if to purl)
slip next stitch from back needle
(off of stitch holder, onto right needle, unknit)
bring yarn back (as if to knit)
repeat from *
repeat this 'pattern' every row.
(after row 1, all the stitches will be worked just using 2 standard straight needles)
this is simple double knitting, and it will result in a "pocket" --you'll be knitting in 'round' on 2 straight needles. you'll have flat Pockets.
(check the pocket every other row or so--if you make a mistake, you'll knit the 2 sides together! if you just did it in the last row, you can knit to the point were they are joined and just undo the stitch, (no need to frog.) the stitches will be a little loose, but will block out fine! --or you can tink.
finish by working a standard bind off, worked tight.
for more on double knitting, check out my blog!
i love double knitting.. simple, and jacquard interlocking double knitting especially!