The base consists of two, 3/8" sheets of aluminum, and a back wall with tapped holes to join them. Using a mill and strap clamps, fixture your aluminum pieces down at a 7 degree angle and mill the top and bottom sides parallel. Then, once you have done this to both pieces, flip them over and draw an approximate line at 17 degrees for the cut on the other side. Cut close to this line using a band saw, and then proceed to mill down to shape. When you have completed milling this last angle, get a 1/8" slotting tool and cut a slot at a depth of 1/8" below this last angle. Do this same step to the other side, but make sure to cut on the opposite side so that both slots face each other.

For the back wall, use a 3/4" x 2" x 1' bar of aluminum and mill both the top and bottom to a 7 degree angle. This will complement your trapezoidal walls. Drill and tap holes at the 1/4, 1/2, and 3/4 lengths along the center piece. Most hole sizes will do, but 6-32 brass screws will look nice on your final assembly. Drill and countersink these same locations on your trapezoidal pieces. On the top side, drill and tap two holes at the top of your center piece, which will mate with the overhanging piece of the lamp (See next step for images).

Lastly, you will need a place to connect your power cord. Jameco offers a nice DC power jack which will fit nicely in your aluminum wall. Use a counterbore to create a depressed region for the nut, and then use a smaller sized bore to make a through hole through the rest of the piece. See the image above for how these parts fit together.