take a t-shirt an cut just below the sleeves, as shown in the pic

u will now have a double square piece of fabric

make some vertical cuts, starting where you just cut, meaning the side that doesn't have the seams

cut about 2/3 long

make the cuts on both sides

pull the strings, and then pull the whole piece so it gets loose

now you will have a tube like piece, open it, put it around your neck, adjust the strings and THERE YOU GO!