I love to use neckties for hand applique, and usually use a stick-on or iron-on shape to define my stitching line.  A method that would stabilize the tie and define the shape at the same time would be to cut the applique shape (reversed) from a soft, light- or feather-weight non-woven fusible interfacing, fuse that to the back of the tie fabric, and cut a scant 1/4" outside the cut shape.  You can then hand-applique and use the interfacing edge as a turn line.