This is a golden yellow long sleeve skinny t-shirt with zipper teeth trimmed neckline that I sewed for my son, it was part of this look. And here's how I made it.
:: t-shirt pattern (I used Made By Rae's Flashback Skinny Tee)
:: long metal zipper
:: disappearing ink marker
:: diagonal cutter pliers
:: liquid seam sealant
Take your t-shirt pattern and instead of following the given neckline, just cut straight across, then cut out your t-shirt.
Take your metal zipper, unzip the zipper so that the zipper pull is next to the bottom stop, just above the zipper pull in between zipper teeth, cut all the way across, this will remove the zipper pull and separate the zipper teeth. With disappearing ink marker, mark the needed length, then also mark one seam allowance length away (towards the edge).