Quick DIY for altering a boring tee. Excuse all the tie dye, I did a large dye session on all my boring white tees...
Quick tutorial below takes 5 minutes.
Cut as shown in the picture. I started in the middle of the sleeve seams but don't cut the sleeves off. Cut along the side seams as far down as you'd like to go. The more you cut the more skin.
Grab the extra fabric and wrap around the top collar part. Pin it to loop around and sew right along the pin.