First things first
Find an object you admire and proceed to completely destroy it.
(Actually I found a dead controller at the thrift store so no innocent lives were lost in the making of this piece.)
To prep it for the plaster pour I filled all the seams, holes and undercut zones with clay. Otherwise I would not have been able to remove it easily from the plaster mold.
Making the Mold: First pour
This was my first mold so lots of trial and error ensued without proper photo-documentation. (Photo 2 is right before the second plaster pour)
This mold is two parts.
I started by clamping the cottle boards in the dimensions I needed, leaving at least an inch on all sides of the controller.
Then I filled the bottom with a layer of clay (just a pound or two) and pressed the controller into it. Then I added more clay around the edges of the controller and box to leave a smooth seam for the first pour of the plaster.
A hearty helping of WD-40 was the final prep before pouring the plaster.
Making the Mold: Second pour
After the first pour set I flipped the whole thing over and removed the clay from the bottom, exposing the other side for pour #2.
At this point I realized I hadn't left any channels to pour the liquid clay in and out of the mold so I made two fat coils out of clay and attached them to the bottom (as shown.)
Another heaping helping of WD-40 and plaster.
To my general amazement, it worked!
The celebration of my genius was interrupted by my professor who pointed out that making a mold for an object that was originally formed in a mold wasn't terribly intrepid of me.
Pressing on through discouragement and fighting the feeling that you're doing something a thousand others have already done before you is critical to the creative process.
I had made a few small impressions in the clay around the controller, hoping they would suffice as registration marks, but they were much too small and popped right off the first time I remarked on their likeness to nipples.
With no registration marks to guide the mold halves together, I just had to be really certain it was lined up correctly and clamped tight before I used it.
Now with my fresh (and still kinda warm) plaster mold, I was ready and eager to make a casting!
Not even a single picture of this part. For shame.
Basically I clamped the mold shut with straps, filled it up with liquid clay, let it stand for about 10 minutes, up-ended it over the clay bucket and let the clay drain out.
I let it sit for another 20 minutes before unstrapping the mold and gently popping it open.
I made ten castings, only three of them were pretty enough to keep.