|This is the chosen one.|
|Put a well fiting pair of shorts on top of it, so you can see where to cut.|
|Pin it on the trousers.|
|Align with something that can be washed off.|
|Now it only has to be washed...|
If you too want to transform a boring pair of trousers into a fabulous destroyed pair of shorts, you can find instructions on how to do it here. It really helped me a lot!