Prepare your cabinets. You can use any two cabinets, as long as they are the same size. Upper kitchen cabinets are best, as they are a good height to become desk supports. Sand and thoroughly clean the cabinets, both inside and out.
Prepare your door. Any old, sturdy door will work wonderfully as a desk surface, unless it has a lot of trim or panels that will make the writing surface uneven. Find an old door with a flat surface. Sand it carefully, especially along the edges, to remove any splinters or rough spots. Remove the door hardware and sand around the inside of the holes left by the hardware. Remove the hinges. Clean the entire surface of the door thoroughly.
Paint both your cabinets and your door. Using the same color will give your desk a uniform appearance. You can also use two different coordinating colors, if you like. You can paint the cabinet doors a different color, or stencil on the surface of the door itself. Make it as simple or as frilly as you like.
Place your two cabinets on a level surface, then place the door on top of them. You want the holes left by the door hardware to be at the back of the desk, away from the cabinet doors, which should be facing the side of the desk where you will sit to work. Lay the door on the cabinets.
Attach the door to the cabinets using a drill and long screws. Be sure it is firmly affixed to both cabinets before attempting to move it.
Move the desk into place. Set up your office supplies. You can use the empty hardware holes as holders for a pen cup and a flower vase.