Tooling boards are - unfortunately - very expensive for a hobbyist like me, especially if thicker and larger pieces are required. Therefore I wonder if there are alternative materials that have been used by other forum members instead of proper tooling boards to keep the cost low.

The obvious possibility is MDF but I'm not sure if there's a way to get the surface good enough. Does anyone have any suggestions?

My plan is to cnc mill the mould directly without making a plug first, but I could change plans for specific reasons.

Kind regards
Martin