Otter's Rock

When my grandma died, she had a huge fabric stash.  Lots of it was either awful, scraps, or half-finished projects from thirty years ago, but there were some nice fabrics in large enough pieces to make stuff out of.  There were also some interesting vintage patterns.  I took the interesting/nice stuff.

Over the weekend, I pulled it out and decided to make some of it into a sundress.  Problem: I needed about 1/8 yard of interfacing, which I do not have.  I live an hour away from the nearest city with a fabric store, and was not about to drive two hours round trip for 1/8 yard.  So I ordered some from fabric.com.  It will get here in 4-7 days.  But it's all cut out and I've done all the steps I can do without interfacing, AND IT'S SITTING THERE STARING AT ME.  The executive dysfunction of autism means that I have two modes: hyperfocused on something, and unable to focus on it without outside pressure.  So not only do I feel really bad about the fact that I can't sew it right now, but there's a decent chance that by the time the interfacing gets here, the focus will be gone and the sundress will sit in a pile on the table for months and possibly never get completed ever.

Also!  This is a light, delicate fabric that ravels if I look at it, and I do not have a serger.  I did the seams of the skirt as French seams (where the raw edges are encased in a sewn channel so they can't ravel), but I don't know what to do about like armhole seams where you can't do that (and in fact need to clip the seam allowance so that there's less bulk and it curves better).  The only time I've done significant work with fabrics that ravel like this was in the costume shop of the theater/dance department in college, where it didn't matter if it ravelled apart quickly, because it was only for stage use.

Googling has not been helpful.  I have seen a lot of seam finishes (some of which are new to me), but none that look like they'd be good for armholes and other curved seams.  Anybody got any advice?