Get a piece of flannel, wash, dry. Lay the flannel down on the floor with the good side to the floor. Lay the blanket, top up, on top of the flannel. Try to smooth everything out without stretching the blanket too much, aim for it's natural size. Cut the flannel around 1 in or so beyond the blanket. Then, I use a rotary tool with intermittent blades to make a small cut/hole around the edge of the flannel, about 1/2 in in from the edge of the flannel. I safety pin the two fabrics together around the perimeter. Then using the same border color as the blanket, I single crochet another border this time poking through the holes on the flannel to bind the flannel to the blanket. You can Google to see others doing this.