Maybe the most boring part of the build would be the router bed. But although its boring, its a very important part, it would be useless without it. The router bed is the place where you place the part that needs machining. Therefor the surface needs to be flat, and perpendicular [...]

I used waterproof MDF as the base for the bed.
On top of that is a 12mm MDF spoil board with a 5cm raster of holes.
The spoil board is the max. work area of the mill, and can therefor be resurfaced if needed.