Welcome and PLEASE practice before you cut into your irreplaceable fabrics. Peckish has a great idea with the simple quilt link. I would use MUCH larger squares than the 3 inch size they used. I would go for 6-8 inches. These will be very thick and heavy, so larger pieces will be easier to handle. Notice that the squares are felted (as ktbb suggested). Scraplady recommended using more than an 1/4 inch seam. You will see why this is a good idea when you star to sew the felted squares together! Use the shirts as the back for the felted squares. No lining (or batting) will be needed since the felted wool is very warm. Keep us posted on your progress!