This 555-based LED flasher is very elementary and easy to put together on a breadboard in only a few minutes, but making a permanent version and precisely mounting it in an enclosure was a challenge and a good learning experience. Because I "winged it" and built this directly from the schematic, the soldered version you see here took at least 2 hours (and much desoldering wick) to get right, and then another 3-4 hours to make the box!
My previous attempts to make enclosures with a freehand drill were very clumsy, so this time I planned ahead carefully and worked on better technique. I used a caliper to accurately measure screw hole distances and bolt diameters, and then drew templates using Microsoft PowerPoint, printed them, and taped them to the box to get the holes in just the right spots. This worked. Amazingly, the scaling of the printer was spot-on, first try. Without a drill press and calibrated stage, I can't think of another way to do this. I'd love to hear what others do.