I also made a puff tie from the same fabric as the waistcoat. Surprisingly there don't seem to be instructions on line to make this so I figured it out from instructions on how to tie one and thought I'd post my 'how to' here.
Start with a two rectangles of fabric - one 9" by 28" and one 2 1/4" by 10".
Fold the larger strip in half lengthwise, right sides together and sew a 1/2" seam around the raw edges, leaving a small gap at the center of the long edge.
Turn right side out. I chose not to press at this stage to give more 'puff' to my tie, you may find your fabric needs it.
Sew a narrow hem around 3 sides of the smaller rectangle. Wrap the small rectangle around the center of the larger rectangle and stitch, leaving a long tail on one side.
Attach to a piece of tape long enough to go round your neck and fasten - I used bow tie fastenings, but you could use velcro or tie a knot at the back.
To wear the tie, tie round your neck with the tail section pointing down. Tuck each side piece under the opposite side of the waistcoat, so that they have a gentle fold at the top and cross over at the bottom. Tuck in securely but not so tight that the puff tie ends up flat. If you wish you can add a tie pin. The 'tail' section should fill any gap between the two side pieces.
Hope thats helpful!