The sketches are made in Autodesk Sketchbook Designer. The 3d model is made in Autodesk 3ds max.
The first step is creating a wireframe basis for the clay model for the form of the pot. The wireframe is hung by a cord slightly lower than its highest point (you will see later why).
Use clay to create the mold around the wireframe. There are some differences in clays. You can buy one for making molds, but those usually have small stones inside. Make sure you keep it smooth in the end. The shape of the clay model should be slightly smaller than you want your actual model to become.
After the mold is finished it is painted with silicone rubber. The rubber is made from a 2 component (silicone) rubber mixture that you can easily order online. The two components should be mixed with a special thickener to make the mixture is paintable.
After painting the mold with the rubber mixture it should be left to dry (the time depends on the type of the rubber you used).