For simple shapes you can use a metal like steel or aluminium sheet to bend and form a simple shapes of flat surfaces and bends.

For complex shapes you usually need proper moulds made from carbon fibre or fibreglass. The fibreglass moulds are much cheaper but will have about 0.1% expansion to consider. 

Easy composites also have their tooling board which can shaped/CNC machined, then sealed ready for use with pre preg.

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