Haha...well mine aren't exactly a 'box, but they work pretty well...
Just make sure there is something in front of it to keep them from rolling the eggs out! Most of mine have the tops on, with a hole cut out, but this isn't one of them.
<edit> sorry about the po'd hen in the pic, she is setting, and really doesn't like being disturbed!
I have the easiest ones in the world, but unfortunately the computer with the picture of it is down right now. I just use plastic milk crates with cardboard cut to fit the bottom and about 5in up each side (to keep the shavings in). Then I just set them on the floor of the coop. Since I put them in, I haven't had a single egg laid anywhere else.
I don't have plans.Like most things like that, I do with whatever scrap I have leftover from something else.I bought the dishpans at the dollar store and built around them.
The nest box is 24"wide x 16"deep.The front is about 24"high and the back is about 40" high.The box openings are about 10" wide x 12" high.
I made the bottoms of the nestbox out of plywood so that when I'm not using them I can pull the pan and pop out the shelf the pan sits on,just to keep them from nesting in the box when I'm using the coop for starting young birds.(teaching bad habits)
It was made out of roughcut lumber left over from my barn.
They sell them in MMM for about $130. but if your crafty you can build a better one really cheap that you'll appreciate much more.
Sorry Mr.Jeff it took so long for your dimentions.I almost forgot til I seen your Popeye avatar again.He's a good man,probably the only reason my youngest will eat spinach. Will