To begin, cast on 21 stitches. Work the lace pattern following the chart repeating rows 1 through 16 until the scarf reaches 54" (or your desired length). Below is the chart of the lace pattern, inspired by a sweater panel from "French Girl Knits" by Kristeen Griffin-Grimes.
The stitches are pretty straightforward with the exception of the three stitch decrease. Here is a picture of the step for slipping two stitches knitwise,
and here is what the stitch looks like after knitting the next stitch, and passing the two slipped over,
I like this decrease because it lets the middle stitch sit in front for a cleaner more even look.
Here is a picture still on the needles (before blocking).