Create DIY for this, I guessing you are going to need to use 2 shirts, cut the one you'll wear with the side slits. Then cut strips out of Tshirt, sew into the inside of the first shirt at the top then weave and sew to the bottom of shirt.
If you are looking for a way to make those old t-shirts look fab again then we have found just the idea for you. This DIY Racerback Tank Top idea is a great way to infuse an old tee with some contemporary style. Give it a shot and see what you think.