What you need is a spare case not one u need if this is your first time lol.
Other wise it will look like this if u rush it.
That was done by a friend that used a dremial cutting tool. That tool is for more advance user.
Ok now u have your image on the case u want to drill a bunch of holes like this.
Once u have holes drilled u want to work from center out i have found it easyier, an cut all the tiny stuff out as well.
Now i use a jigsaw with felt on the bottom of the plate because if felt now there it will scratch the case and that means alot more work to fix.
After all cut out it should look like this.
Now you are going to want to flip it over and start pulling of the support braces so your plexy glass will lay flat on the back side. Hear is what u should be removeing.
Now that all that fun is done the rest is cake. U will want to clean all the edges with at least 320grit or higher so it dont leave scratches. And next prime an paint your case to your likeing.
I hope this helps the new modders and u will learn diffrent tricks along the way.
U might want to start with an easy cut out like this.

Remeber measure twice cut once can't glue peices back lol. Hope this helps