As promised, not long, not exciting and pretty simple really
First the foam, I have both blue and pink foam in the store cupboard ........ both are Styrofoam types. You also may find offcuts of the yellow type with a foil backing around building sites
For this job the pink was a bit better as it had a slightly coarser grain structure.
I then cut a number of slabs of the foam block , I used a band saw, the widths of these varied from 1 mm to about 5 mm
Note, I deliberately made no attempt to cut these slabs with parallel edges, if anything I was looking to try and vary the width across the length of the slab.
These slabs were then cut into strip all about the general width/depth of the wall
These strips were then cut into the various lengths I had calculated for a scale 1/35 wall, mixing the lengths with the various thicknesses.
I then "textured" the part of the foam that would show on the external side of the wall ... now you could knives, toothpicks, etc , as I don't bite my nails I found that pinching bits off with my thumb nail worked fine by me.
Now to build, on a base of thick card I laid down a strip of double sided tape .... I used d/s tape as I did not want any glue seepage to spoil the look of the wall
The base stones were laid down on the d/s tape. Follow the real thing here and use your thicker strips in general at the bottom of the wall, working to medium and then the thinnest ( and real life the heaviest blocks at the bottom lightest blocks towards the top ) This is not a strict rule and you need to use thinner strips to level out the wall as you build. I find it useful to insert a large block in odd places to ensure variety ( in the real walls I believe these heavier blocks are inserted to span the wall front to back to build its strength and stability)
As you can strips of D/sided tape is used between each layer of blocks, and the wall built up.
When the wall had reached a height I was happy with, in this case a scale 4 feet in 1/35 a layer of very thin blocks were added at the top to provide a reasonably level surface for the coping stones to be then added. I also added a strengthening strip of card on to the rear of the wall.
Style size and shape of these copping/cap stones appears to be one of the identifiers of the locality.
The finished wall , with gate post added.
That's it, as I said fairly simple, cheap material and very few tools needed.
Painting details may or may not follow