Typically CNC cut from 18ply or mdf from very accurate plans. They can be shipped completed or flatpacked for user assembly. I can also produce the foz jig itself if needed.
These are typically layered mdf, split in two halves for easy disassembly after the soundbox is 'boxed up'. They come with inside cauls for clamping the sides inside the forms while the neck and tailblock are attached. They also come with a smaller clamping setup for the waist which is the removed through the soundhole after it is boxed up.
We can also supply a complete set of forms, individual forms, templates for any model where the plans are available.
Pictures are a range of forms/templates i use myself. They are accurate and reusable many times over if well cared for.