For starters, square up your fabric and cut to size, making sure you fully remove the selvage. I made this blanket out of 2.5 yards of fabric for a twin bed. Since we're doing a single fold hem, take care to make a nice straight edge.
Once your fabric is ready, mark 1.5" all around on the wrong side of the fabric. Fold the edge over to meet the line and pin in place. Mark to the edge, but leave the corners open.
Trim the corners at the diagonal, leaving a slight allowance. Fold right sides together so that the two points meet. Sew along where you've just cut. Unfold, reversing the corner, and pin to the wrong side as shown.
Select a stitch to finish your blanket with, and ensure the stitch width is wide enough to consistently catch the unfinished edge. I used a decorative stitch for this blanket, but a simple zig-zag or blanket stitch would work fine for this. Sew over the unfinished edge being careful to keep the edge at the center of the foot and the fold even with your 1.5" mark. Trim edge as you notice any uneven cuts.
I rolled the blankets and secured with a decorative bow before giving these to the birthday girls. Doesn't that look nice?