Bill -
I didn't have formal plans for mine. It's basically a box with a footprint larger than my contact frame with blacklight bulbs inside. The sides were made from 1/2" MDF, with a top made from a piece of plywood I had left over from an earlier project. I used six spiral CFL blacklights with ordinary "edison" screw bases in plastic lampholders from Home Depot. After reading a lot of stuff on the web, I spaced the bulbs on 6" centers, and set the height of the unit such that the bottom of the bulbs was 6" above the top of my contact frame. I also mounted a sheet of bare aluminum flashing material under the lampholders to act as a reflector.
I opted for the "pizza oven" design in which the sides of the box extend all the way to the bottom of the box, and with a door (hinged on the top) in the front through which the contact frame can be inserted. With that design, there is no spillage of UV light into the workspace. I think that is important because UV light is a known cause of cataracts (just had the first one removed, so I'm more aware of that problem right now), and also by eliminating UV spillage, I minimize the risk of fogging materials that I am preparing while using the UV box.
I mounted an exhaust fan in one corner of my unit, with a louver in the opposite corner to provide ventilation for the bulbs. Heat buildup will reduce the life expectancy of CLF bulbs, and since they aren't cheap or easy to find, I decided that was a wise investment.
The major expense is the bulbs. I bought mine
here