This was sooo easy.
It's based on the threadbanger episode ft laceel. you basically take a tshirt that fits okay, cut off the sleeves and the collar, open up the shoulder part, put an elastic in the bottom hem, try it on (what was down, becomes up) en pin the band so it fits.
Take it off en sew the elastic with a zigzag.
hem the bottom (which used to be the top), make a bow and sew it on.
Try on the top and admire your fabulous work. =)