Plain Seam with Clean-Edge Finish
Sew a Plain Seam. Fold garment with right sides together and with bottom seam allowance (raw edge) folded under, the upper seam allowance flat.
Fold over the edge of the upper seam allowance 1/8 inch. Stitch close to folded edge. Repeat on other side.
Press seam open.
The Book says: this seam "helps to keep the seams flat and prevent fraying. It also helps finish the raw edges of open seams."
Obvious lesson I learned: make sure you fold the garment (or scraps in my case) in half for both sides. I got lazy on the second and didn't fold in half, resulting in stitching the seam allowance to the top, right side of the fabric. Genius = me.