Cut the plywood lengthwise down the center. This should leave you with two pieces of plywood measuring 2 by 8 feet. You only need one of these pieces for the desk. Although you may opt to use the entire piece of plywood for a larger desk.
Apply a stain to the plywood, and crown molding if you choose to match it with the filing cabinet.
Place the plywood on top of the two filing cabinets.
Position the filing cabinets evenly on either side of the plywood. There is no need to attach the plywood to the cabinets because the weight of the plywood and the computer components will hold it in place. If you choose to do so, simply install L brackets on the bottom of the plywood and the side of the cabinet.
Cut two pieces of crown molding to fit around the plywood. You should have two pieces of 8-foot sections, and two 2-foot sections. Each section should be cut with 45 degree angles at the ends, so when fitted together they create a perfect corner.
If the whole sheet of plywood is used for the table top you will need three strips of crown molding. Two 8-foot sections, and two 4-foot sections.
Attach each crown molding piece to the plywood. Align the molding flush with the top of the plywood. Insert nails throughout to hold it in place.
Apply wood putty to the crown molding to cover the nail holes.
Color the putty with a marker to disguise the flaw.