Making an army of Gromit's (Claymation Mold making)

Step 5 Bury your Buddy.

Remove any parts of your figure that you do not want to duplicate (in Gromit's case his eyes and nose).

Use the petroleum jelly to lightly coat the back of your figure.
(Your original figure is likely to need cleaning and touching up after the mold creation process, petroleum jelly makes this an easier task as it acts as a lubricant/mold release).

Lay your clay figure backwards onto the base of clay pellets.
Gradually build up the clay pellets around your figure until it is half submered by them.

When the clay pellets are burying your figure to half it's depth start to apply thin smooth sheets of clay onto the pellets.

Push the smooth clay up to the very edges of your figure making sure they form a tight seal around it. Make sure there are no holes that mold compound can run down.

Now push four 1/2" ball-barings half-way into the clay (one in each of the four corners of the clay) and leave them there. This creates 'keys' in the mold which allow it to fit back together again once the clay original is removed. (You can use anything to make a key, I typically make protruding clay ramps on the clay surface as keys).