This type of case will not protect against drops or falling but will protect against smudges and scratches.
Step 1: Practice
I mad ea few mistakes with the dimensions in the one I made for this tutorial. So be careful and be willing to make more than one.
Step 2: Get the Dimensions of Your MP3 Player
Be careful while folding and etching. Doing it wrong makes the end result useless. Don't be afraid to try this multiple times. It's worth the effort to get it right and not mess up your finished case.