Human forms displayed in Pompeii were created by pouring liquid plaster into the voids left by the decomposed bodies of people who perished during the eruption of Mount Vesuvius nearly 2,000 years ago.
People who died in the volcano Vesuvius in 79 AD are often presented with the scene at the top of the attached pH๏τo as actual evidence of the catastrophic disaster, and many people who see it tend to think that human bones are found in that way, but as I have said many times, that is actually a plaster statue, and while human bones are not excavated from the site, most of them have been almost completely eroded by the volcanic ash.
Instead, the human bones leave a hole in the volcanic ash pile where the person was, and when the excavators take advantage of this, they pour plaster into the place where the person was, filling only the empty space.
That method was developed in the 19th century.
Simply put, the plaster was poured using the casting technique to recreate the appearance of the Pompeii victims.
The attached pH๏τo below is a diagram of the process of creating a human body by pouring plaster.
In that scene, it was set up as if human bones were left, but most of them had been eroded away.