A big thank you to everyone for your comments and suggestions!
I just finished it a few minutes ago...
Click pics for a larger view.
And I'm very happy with the difference between yesterday and today's version. It turned out much bigger than I expected. I thought it would be on the smallish side with only 12 squares, but it's a full-size blanket.
I went with joining the squares in linen with a single crochet, and then did single crochets all the way around also in linen. I picked a border out of Jean Leinhauser's 50 Crocheted Afghan Borders (#47), which I got in the mail today. I omitted the last round of the border which would have been done in dark brown, but I thought it was a little too much. The small amount of brown is perfect.
I really enjoyed this project.