Things you need:
Old jeans
Scissors
Unipin or any kind of marker
Raffles Pattern
Ruler
What to do:
Lay down your old jeans and measure the length of the shorts that you want using a ruler and unipin to mark.
In a paper, cutout a raffles pattern and trace it on the top of the jeans.
Last, cut it out using the scissors.
That's it. so simple and easy.
Enjoy! :)