Locate the materials to create your desk. Your door, which can be hollow-core or solid wood, should be 28 to 30 inches wide. The standard length is 80 inches, and this will be the width of your desk. The door might be left over from your own building project, or you can find one cheaply at businesses that recycle building materials.
Locate two metal file cabinets. These can be found at thrift stores or online. A business closing its doors, or upgrading office equipment, might be willing to donate or sell cheaply two file cabinets. Check with businesses that recycle used office furniture. These cabinets need to be the two-drawer vertical style, 28 inches deep.
Prepare your door, which will be the desk top. The door may have a hole that was used for a door knob. This can be plugged with a circle of wood, or left in place to accommodate computer and phone cords. Sand the door surface with 120 grit sandpaper, and sand smooth the corners and edges.
Paint the door, if you wish, with a glossy paint. You can use a brush for the door, but use spray paint if you color-coordinate the door and file cabinets.
Allow the paint to dry, then position your cabinets where you want the outer sides of your desk. Place the door on the cabinets. If your cabinets are 28 inches high, the added height of the door puts the desk surface at 30 inches above the floor, standard for many desks.