you will need:
- some yarn (3 different colours if you want a cool strap!)
- a safety pin
- a pillow
- and braiding skills!
all you pretty much do is braid the yarn (i pin the beginning end of the braid onto a pillow so i can get some tension) and tie it around your uke!
i used about 53 inches of yarn to make mine ( I'm about 5'1" and it fits me comfortably, but if your taller you may want to use more!) also remember that when you braid it you loose some length so you also might want to add a few inches (about 2 or 3) and if it ends up being too long you can just snip it off :)
heres some pictures i took of the strap, and i made a yellow, white and blue one for my friend caitlin!