Primrose is worked from the top center outward. Additional stitches are cast on and the border is worked while attaching it to the shawl as you go. It's so efficient. :)
Borderline: Taking Lace Borders to the Edge of Shawls. You can get more details on the e-book here.
I am so in love with the shawl. I knit this one out of Knit Picks Gloss Fingering, but I think it would look amazing in any fingering weight yarn. Maybe some Hazel Knits Entice MCN or Anzula Cloud?