I see this dress pinned daily on pinterest. It's a simple design and all it requires is a tie dyed XL tshirt.
I just did my yearly shibori indigo dyeing and made this dress from my husband's shirt.
I went with a basic tie dye print my son made for me.
Starting with a much larger than you tshirt...cut the sleeves and remove the collar.
Cut as such to create a halter.
Finish the arm edges or not…Fold over the collar edges and iron or pin.
Sew 1/4 inch edge for the front halter.
For the back cut a slit and then sew the edges over 1/4 in.
Weave a string through with a safety pin. I used a strip from the left over sleeve.