I found this pattern overly complicated but eventually ignored it and just did what seemed right. Added a border, as follows:

Row of DC in White along long edges, followed by round of variegated yarn used in main part of blanket, then round of an odd ball of purple/mauve that I found in my stash. It had no band, but I think it was an acrylic. This was followed by a round of popcorns in the variegated yarn, then a round of sc in the purple.