One good sized stainless steel or enamelled saucepan.
A mould to pour/scoop the whipped soap into whilst it sets. A wooden or cardboard tray or box lined with grease-proof paper or siliconised baking sheet is great. Silicone cake-baking moulds are also suitable, as are some other forms of plastic moulds such as ‘tupperware’ containers.
The solution (now known as Lye) will heat up to nearly 200oF and will need to be left to cool.Important… If the room temperature is generally warm it will help to refrigerate the lye to ensure it’s completey cold before use.
Above shows the filled mould having had the soap worked into a finish that looks a little like a meringue or whipped cream, then having been divided by dragging a spatula through whilst it’s setting.
After leaving the mixture to saponify overnight until it becomes a light, whipped solid you can cut it into chunks as shown as an example of how it might be displayed or sold.