Starting in the 2nd chain from the hook, insert your hook, yarn over and pull up a loop, *insert your hook into the next chain, yarn over and pull a loop. Repeat from * two more times, (or until desired height of stitch.) Yarn over and pull through two loops 4 times or until you have one loop remaining on the hook.
To begin the next stitch, insert hook under horizontal bar, YO and pull a loop back through. Insert hook under next horizontal bar, YO and pull a loop back through. Continue inserting hook under each horizontal bar in same manner until you reach the chain. Insert hook into next chain, YO and pull a loop back through. Yarn over and pull through 2 loops until one loop remains on hook. CH 4 (or however many you need to match the height on the first row) and turn.
REPEAT ROW 1
See video tutorial below.