Step 1: Supplies.
Ruler,(or good judgment of measurement, or an actual tie to measure up to.)
Step 2: Trace, cut, decorate, tape.
Take 2 pieces of tape. Make one double-sided, and the other leave alone. Take the double sided to attach the regular piece of tape to the back of the tie. You have sticky on the double-sided and sticky on the regular shwing. Then, you can more or less clip it to your shirt. :)