At first is looks like you’re in for a full body cast, but actually there are just three smaller casts made, one for each hand and one for your head. After molding these high-value parts the body was filled in by placing expanding foam, then carving the hardened result to a fairly accurate body representation.
The carving doesn’t have to be perfect. That’s because much of it is covered by the front half of a dress which is immortalized in the sculpture with a thorough soaking of casting resin.
It’s a huge project, but here’s the instructions if you want to take it on.