This must have been one of the shortest lived items on my Round Tuit pile as I managed to get the Arduino driven temperature display boxed a couple of days ago. For the rectangular hole in the plastic front I drilled small holes at the corners and used a Rotozip to cut the lines. Finally finished with a file.
Pity about the small nick in one corner. I would dearly love to have a laser engraver / cutter machine. The display matrix is behind two acetate sheets, one red, one green so only the illuminated LED dots show against a black background.:
One added extra was an LDR (light dependant resistor) which can be seen under the display. This monitors room light levels and is used to switch the LEDs to a brighter level in very bright lighting conditions. The unit is powered from a 5V wall wart. I'm very pleased with the readability of the large display from anywhere in the room.