After hoping that letting the fabric and the foam cushions sit near each other for a while (months) would somehow result in the covers sewing themselves, I finally decided that was not working. I can sew. I grew up sewing all my own clothing. And I hate sewing. I genuinely enjoy many household chores like cooking and don't mind many of the others. But sewing I have never enjoyed. However, after getting tired of looking at the ugly shade of green foam sitting there and getting a quote that someone else would sew them for me for about $400, I decided I'd better just do it.
Thanks to a friend letting me use his sewing machine and a few evening of work, they are finally completed. Not the most professional job I know, but I am satisfied with the way they turned out. There are zippers in each one so the covers can be removed for washing or to replace the foam eventually.
I am now much happier with the appearance of my couch for sure!