I bought some XPS foam tiles from Firedragon Games which are pressed with a flagstone pattern. Good service and tiles are £2 each and will save hours of etching foam with a biro!
The tiles are 11" across (285mm) so I am using that for my tile size with the intention of making 9 tiles initially and then exapnding to 16 for a 4' x 4' (ish) table.
Here is a test painted tile:
Which has been washed with Supershader Black and then drybrushed in various greys up to an almost white. Really brings out the tiles quite nicely.
Also shown are repurposed LOTR Balin's Tomb scenery as scatter terrain which have been drybrushed lighter and had snow painted around them.
So, 8 more tiles to paint and 9 to stick to lasercut MDF tiles, then I can layout some terrain and see how much more I need to do.