Excellent game table, thank you for passing on the link!
All of the following are guesses.
The snake fencing can be made with balsa or bass wood sticks cut to sizes appropriate to the scale. Glue with PVA (white household glue or yellow carpenter's glue) or super glue.
I'm guessing the rock fencing is made by piling aquarium gravel or large model railroad ballast (probably crushed coral since that gives nice angular scale rocks) on beads of PVA glue, allowing to dry, then repeating more layers of PVA glue / scale rocks until the desired height is reached. Then painted of course. It has that characteristic "piled" look instead of stacked which we would expect for an in-scale fence.
The fields look like several types of ground foam mixed together, and based on the color of the rocks and the mix of ground foam, it looks like he's following Woodland Scenics model railroad techniques for applying ground cover. So you could look for tutorials on their site, woodlandscenics.com
The roads look like garden dirt sifted through a fine screen to remove larger pieces. I could be wrong, it could be a ground cover product. And road ruts drawn in by dragging a paintbrush handle.
I also can't tell from the pictures if the fields and road are fixed in place (with scenic cement or matte varnish) or left loose and swept up after the game.
He mentions his friend Lord Ashram came over to take pictures. I thought I recognized that name; he has his own blog site, Lord Ashram's House of War: link and also is a TMP member: TMP link .
On Terragenesis, member Tob has been posting a work-in-progress discussion about making split rail / snake fencing, might be worth looking at: link
