Cutting and sewing random, gently curved pieces is easy with neckties because they are cut on the bias and even gently curved cuts, while not true bias, are close enough for easier fitting.  To prepare two pieces of necktie for curved piecing, spray and press first with Mary Ellen's Best Press, then overlap them on a cutting mat (1-2" of overlap is enough) and cut through both layers in a gentle curve.  Remove the excess of upper overlap and mark the exposed edges of tie at several matched places.  Matching the marks, pin right sides together and sew in a 1/4" seam, matching the raw edges as you sew.  Press seam to one side, clipping if necessary.