Craft Buds has been doing. I had narrow strips left over from the Craftsy QAL that worked great for it.
The tutorial (you can get it here) calls for making the pleats less uniform, but I just could not bring myself to do it that way. I kept going back and fixing it until, eventually, the pleats were pretty much uniform. In addition to the downloadable tutorial, there are posts covering each aspect. I probably should have paid more attention the the casual pleats part, but, actually, I'm happy with the finished product.
To show you how simple it is, here is the front panel prior to pleating.
The back has two overlapping pieces to slide in a pillow. If you've got some little scraps you can't bear to toss out, this is a great way to use them up.