Step 2: Molding
I used plaster to create a mold for the latex to be poured into (specifically, Hydrocal). First I needed to create a well for the plaster to be poured into. As the plaster started to set up, I could mound it up on top of the sculpt, which meant that I didn't need to create retaining walls that were very high.
I used WED clay to create a base and walls along the sculpt. Next, I mixed up the Hydrocal and spread it along the sides of the sculpt, and drizzle over the top. It's important to do this slowly and carefully, as you want to make sure you pick up every detail.
After pouring the initial coat of Hydrocal over the sculpt, I continued to mound it up and create a flat top to the mold. When the mold is turned over, this creates a flat base which makes it easier to manage.