I should call this the monitor, printer, speakers, phone shelf because I have all of that on mine.
OK, next step is to assemble the monitor shelf. The diagram on the right is a top view of it. It is 48" long, 6" high (plus the thickness of the top piece of plywood) and 15" deep. I attached 15" pieces of 1x6's to my plywood piece at each end, a 46 1/2" piece of 1x6 at the back, and three 14" 1x6's evenly spaced in the middle.
As I mentioned before, the middle pieces should have worked out to 14 1/4", but that was too long, I don't know why. Your results may vary.
I used Liquid Nails to set the pieces together, strips of molding on the ends to make sure it was square, and short pieces of 2x4 in the corners for strength & stability. I put screws through those in addition to the glue. I put short pieces of 1X4 in the back corners of the middle braces, & used glue & screws on them. I probably overdid it, but I'm tired of the lightweight crap "furniture" on the market, & if I'm going to build something, at least I can make it sturdy.
Each cubbyhole is full on mine. The one on the left is holding paper for my printer. The next cubbyhole has CD's in it, the height of the shelf is perfect for CD's. If you have a lot, you could use all 4 cubbyholes for CD's. The third cubbyhole I use for pens, notepaper, etc. The fourth one has file folders in it.