Here is a really cheap, simple "file tray." I know it's not fancy, but it's functional and cost me a roll of duct tape. And not even that b/c I didn't use the whole roll--not even half! The cereal boxes I don't count, since I'd have those anyway. I just saved these from the dumpster. :-D
So, did you know that you can get duct tape in all kinds of pretty colors and designs now? Not just the dull silver that's been around forever. So, first thing you want to do is pick out a design you like. As you can see, I favored the blue with white flowers. You can also get it in sheets, by the way (the size of a normal piece of paper). But I found the roll to be the more practical and versatile option.
Besides the tape, you will need empty cereal boxes and scissors. I have for boxes in the pic here, but decided to just do three. 
First, you will want to trim the boxes so that they are the same length. Next, you will start wrapping tape around the boxes to hold them together.
Repeat this step until the whole box is covered. I didn't actually cover the back or the bottom. I figured those parts wouldn't be visible, so why waste the tape? But you can do that if you want to!
And there you have a cheap, simple file tray. Nothing fancy. Maybe something you don't want to show company. Maybe close friends who know how quirky and frugal you are. :-P Maybe one day I'll venture to make a lid for it for storage. I'll be sure to let you know when I do.
