Half Double Slip Stitch (Back Loop)
YO, insert your hook into back loop, YO, pull up a loop and pull directly through two loops on hook
CHAIN
Any number
ROW 1
Starting in the 2nd chain from the hook, *YO, insert your hook, YO, pull up a loop and pull directly through two loops on hook. Repeat from * in each chain. CH 1 and turn.
ROW 2
Starting in the 1st stitch, *YO, insert hook into back loop, YO, pull up a loop and pull directly through two loops on hook. Repeat from * in each stitch to end of row. CH 1 and turn.
REPEAT ROW 2
See video tutorial below.