I bet some find it hard to stomach buying $27 plastic panels for a $10 plastic case when debating a few bucks differences in micro-controllers.
That said, my building brother, I too get anxious on cutting holes. We don't know what tools you have, and given the question, assume not a mill or a drill press.
What I would do is cover the front side of the plastic panel with blue 3M painters tape. Scribe the centerline for the holes directly on the 'inside the box' portion of the plastic where it won’t be seen. I use center drills to start the holes (they are cheap), if you don't have center drills, use a small drill bit. Once the initial undersized holes are cut, flip the piece over and drill from the 'outside the box' side so if you get a chip out it won't be seen. Best to start small and step up to one drill bit less than size. When drilling, secure the plastic panel over a scrap piece of softwood, and make this a "pine board project." With thin plastic and drilling with hand tools, I find that the final drill bit size is best done by hand. I have an old pcb hand nibbler tool ($10?) for cutting somewhat square holes with patience. Just slightly undercut the rectangle for the LCD with the nibbler, remove the tape and finish out with a bastard file and sand paper. If all goes wrong, you can still try 2 more cases or spend the $27. Also search this forum for good ideas on printing a full face 'label' which might cover up the sins of a nonperfect cut. Stain grade or paint grade? My wood working Grandfather taught me very early in life that a coat of paint covers a multitude of sins. Nothing ventured, nothing learned. Maybe someone else has some tips.