Shawl is started with a garter stitch triangle, with bands of alternating direction garter stitch.
Photo garment was knitted with two skeins of hand-dyed Jilly that didn’t quite match, so the skeins were alternated in the bands to accentuate the slight difference in color.

If you want a larger shawl, you can add more bands (you’ll need more yarn for the body and border). The border repeat is set up so that it matches the number of stitches that will be added with the bands, you’ll just be adding more repeats of lace.