This idea is curtesy of my German grandmother, she said she had them in every colour back in the 60's when you could buy them in stores. The thing is, it's SO easy to do your self. I put it into two simple illustrated steps.
1. Find a shirt, this can be any shirt, it doesn't even have to fit you (opp shop is a great place for this if you don't want to chip chop your wardrobe)
2. Cut the shirt (as per dotted line)
*If you have a sewing machine, I recommend hemming it, if you don't, don't worry it won't fray much if at all.
And your finished!
This is how I wore my shirt collar:
Black silk shirt: Friend of Mine
Rose-gold necklace: Sportsgirl
Shorts: Free People
If you do this DIY I would love to know how you go!