More ideas from Kaja
really cool way to transform an old boring shirt into something fun! Via Sortrature Cool DIY T shirt Redesign Ideas

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.