When folding the cloth over in preparation for the second stitch, the creases should be ironed flat to keep the seams neat. Since I didn't have access to an iron during this project, I just creased the edges with my nails, and the muslin was relatively receptive to this.

The following few photos show a finished French seam from a couple of perspectives: the first image shows the raw edges hidden inside the fold of the seam, the second image shows the result on the wrong side of the fabric, and the third image shows the result on the right side of the fabric. This seam is nice because stitches are completely invisible from the right side, although I thought that even the wrong side was kind of nice and could potentially be used as an accent.