I'm a kind of traditional person who firmly believes in tying your bow ties. I tried making my first bow tie ever, and I'm proud to say that it turned out all right :)
Bow ties aren't hard to make at all, although sewing them by hand can take a while o.O But imagine the awe of your peers when they realise that your slightly-dodgy-bow is not only self-tied, but hand made!

Step 1: Required Stuff

For a bow tie, you need:

Basics ---> Needle + thread + sewing machine + measuring tape + scissors + pins etc
50cm x 50cm of woven fabric (at least)
Thin interfacing
Bow tie pattern

Traditionally, bow ties are made out of silk, but I didn't really have any silk on hand. I used a thin cotton poplin because it's easy to work with. I also didn't use interfacing, because I don't have any, but it's much better if it is used, because it makes the bow look stiffer and prettier when it's tied.

Step 2: The Pattern

To get the right shape of the bow tie, a pattern is the best. There are quite a few patterns wandering around the internet, but I've included the pattern that I drew up and used. It includes 1cm of seam allowance, so if more is necessary, it needs to be added on. The pattern roughly fits a 43cm neck, so don't forget to adjust it to size before you cut out the fabric.

When printing the pattern, make sure you scale the print at 100%. The pattern should be printed on A4 paper, which is 8.27x11.69 inches. Cut out carefully and then tape the two As together. The arrows on the pattern indicate the grain line. Bow ties should be cut on the bias because it makes them easier to fold.

Align the pattern piece on the fabric so that the grain line is either parallel or perpendicular to the selvedge. Either fold the fabric behind the pattern twice so that when it is cut, you get 4 pieces at once, or trace out the pattern 4 times individually (as I have done).
I made the lining out of the same fabric, but if you wish to make it a different fabric, cut two of the lining and two of the outer fabric.

If you are interfacing, cut two pattern pieces out of interfacing and iron them to the wrong side of the lining.

Bow Tie Pattern-final.pdf
Download

Step 3: Forming the Long Pieces

Take the two lining pieces and align the slanted ends as shown in the first picture. The pictures explain better than I can.
Sew the pieces together 1cm from the edge. Repeat with the other two pieces.

Step 4: Sewing It All Together

Pin the two long pieces right sides together. Sew all the way around, turning the corners sharply and 1cm from the edge. Make sure to leave a gap about 10cm long so that you can turn it inside out later. Trim the excess so that it's only 5mm or so. Cut little triangles where the bow is convex, so reduce the bulkiness.

Turn it all inside out, using scissors/a capped pen/a chopstick to poke the corners so that they're sharp. Iron it all out so that it's nice and flat :)
Stitch up the opening (ladder stitch is the best) and iron some more.

Step 5: Tie Your Bow Tie

Hurrah! You're done! Now, to tie your bow tie...
I apologise for my terrible bow tying skills. In my defence, this is my first time tying a bow tie. Hopefully, my bows will look better in the future, as I will be practising lots and lots with my new bow!

Since I'm still a noob in terms of bow tying, I suggest looking elsewhere for those instructions. There are some 'ibles, right here on this site. Personally, I like this one by BigCoCo. I still think that videos are the best though, so try Youtube.

Goodluck with your bowtie making, and thanks for reading :D