There are several means of making a mold for porcelain. In this Instructable I will be using a positive of the desired piece to produce a negative void in my mold.
Step 1: Put Your Idea to Paper (or Monitor)
I used Google Sketch up to render my model. Not an intuitive program, but it's free. Being cheap, that's the right price for me. Your drawing needn't be spot on. I only put measurements in mine for general reference. You just need an approximation to give you something to work by.
Step 2: Making the Positive
In this case, I turned this out on a metal lathe. You may want to carve yours out of wax or soft wood. I have even used auto body filler to make a rough shape and refined it later with a rotary tool. Lost wax is nice for detailed work. My next Instructable I will show how to make the mold of the positive. It will be a weekend long project that will require lots of photos.