The First part of the process is to make a wire armature.
Second, you put plasticine over that armature and put in whatever details you want to show up. In this case, I left out the rivets because I'll actually drill them into the mold.
Then, you put a base down of regular clay (thanks Justin) and mold it up to halfway around the body. You press in a ball halfway up to create a key that will make the mold lock in together when you snap the parts together. This is the tough part and I'm still trying to figure out the best way to do this. I thinking if I turn the clay into a thick slip that it may work better but will take longer to solidify.
After that you build up your walls, in this case I used LEGO because it allows for a perfect box. I'm an engineer so I like square things.
Then you pour your plaster in and make one half. After it dries, you pull out the clay, pour the other half and then you have a mold!
This is a photo of the internal armature of Chris Bot.
This is a photo of the clay model of Chris BotThe final puppet will have the two cameras mounted on itself and the appropriate rivets to hold him together.