Place the 60-by-22-by-¾-inch oak plywood on a worktable with the good side facing down. Remove the drawers from the two 18-inch-wide oak file cabinets. Turn them upside down and put them on the piece of plywood with the fronts facing you.
Align the file cabinets with the sides of the plywood. Push them away from you so the backs of the file cabinets are even with the 60-inch edge of the plywood. Secure them to the plywood with the 1¼-inch drywall screws.
Set the piece of plywood against the backs of the file cabinets. Raise the plywood up so that it is even with the bottom of the file cabinets and secure it with the 4-penny box nails.
Turn the cabinets upright. Measure from one side of the top and make a mark at 30 inches. Next, measure from the back of the top and make a mark at 3 inches.
Drill a hole in the top with the 1½-inch paddle bit. Install the drawers back in the file cabinets. Measure and cut the oak veneer edge band 1 inch longer than each edge of the perimeter of the top.
Adhere one piece at a time with a hot iron, holding even with the bottom of the top. Break the ends of each piece over the corners before adding the next piece. Sand the veneer with 100-grit sandpaper.