How to do it
Ch 3, YO, insert hook in 3rd ch from hook, YO, pull up a loop, YO, pull through 1 loop on hook (ch made), YO, pull through 3 loops on hook (first FHDC made), *YO, insert hook into the ch made at the base of the stitch, YO, pull up a loop, YO, pull through 1 loop on hook (ch made), YO, pull through 3 loops (second FHDC made). Rep from * until you have the desired number of stitches.
Visual Steps
Ch 3
Yarn over
Insert hook in 3rd ch from hook
Yarn over
Pull up a loop
Yarn over
Pull through one loop on hook (ch made)
Yarn over
Pull through all three loops (first FHDC made)
Yarn over
Insert hook into the ch made at the base of the stitch
Yarn over
Pull up a loop
Yarn over
Pull through 1 loop (ch made)
Yarn over
Pull through all three loops (2nd FHDC made). Repeat from step 10