Although this looks like a model of the M4 elevated section it is, in fact, the start of the process of forming the trackbed around the S bend on Bron Hebog.
The plywood which you saw marked out in a previous post has been attacked with a jigsaw and raised up on a procession of piers, carefully graduated to maintain an even gradient.
In the view above you can see that Himself has managed to cut the railway alignment and the farm track out of the same sheet of wood.
The railway is the section at the top of the image and the farm track is below it.
The bit where they are joined is an occupation crossing which in due course will have to be festooned (or should that read ffestooned?) with all manner of warning signs and fences which is why the wood has been cut much wider so there is something solid to anchor them all into.
These pictures demonstrate the clear advantages of an open frame baseboard design as opposed to trying to build everything up from a solid base, although even we have to admit that it does look more like a motorway than a model railway right now.