I tried everything to keep from taking this next step on "Off the Grid" but I finally had to take a deep breath and just do it. Here you see my sample testing different couching stitches, and then the real thing done on the flap. The Sulky tearaway stabilizer is still attached to the flap.
Why was I hesitant to do this? I have just one piece of this fabric. If I botch that corner, the whole thing goes in the dumpster. I don't like not having safety nets. I don't like having to decide on stitches. I'd rather the yarn magically adhered itself to the edge of the fabric!
Here's a close up. I tried a three-step zig zag, regular zig zag and a several decorative stitches before I settled on this blanket stitch: two stitches forward, one back and forth to the side. The stitch is not the thing, in this case, but has no choice but to be visible. These straight up and down stitches are a good match for the grid in the fabric. The edge of the fabric was Fray Checked in advance so the couching stitch wouldn't have to double as a way to keep the edge from fraying.
This went off without a hitch, lightening my mood exponentially. But I almost immediately began second guessing myself. I want that flap to hang loose, drape on its own. I'm hoping the slight addition of weight from the yarn will help that. The second guessing is wondering if I should have bonded some interfacing to the underside anyway. I can see where this could be a problem if I end up shipping it somewhere for display. Well, I guess any addition of a stiffener can happen almost any time.