I set out to create a bow-tie recently, and it did not come without some challenges, and some insight.
I have a few bow-ties already, and I love the straight shaped ones, so I used one I have and created a simple pattern from it. Just adding 3/8 of an inch to all the sides and making it long and straight was all there is to it. When cutting the fabric, cut on a BIAS! this is very important to the final product, a tie that ties well and stays tied through the night (tie, once more for posterity, tie).
then attach some interfacing, this is where trial and error came in. I found it very difficult to use fusible interfacing, it made the final product rough and ugly on the outside, so for round two I went with the sew in kind; like before cut it out on the BIAS, and only one piece of interfacing is needed if its the sew-in kind.
sew it together, and turn it right side out with a chopstick or similar, give it a really good press with lots of steam, and instead of finding hardware to make it adjustable, I just tacked the ends together with the sewing machine.
Now cut a rug and make girls (or boys) dream of you (or just pretend they are to boost self-confidence on said rug)