I haven't actually played it yet, but I've seen the videos, read the rules, and it looks fun. Not only that, but I already have a sizeable collection of painted samurai to use!
The battle board was mapped out using isometric graph paper to set the grid, then it was cut out of a piece of 1/2" (paper backed) foam board. Carefully flocked, the edges painted to clean up a little, and little felt pads added to "float" the board a little (and level it out and protect whatever surface it's sitting on.)
The rocks were carved from blue insulation foam and painted in a couple layers of wood glue to add durability. The shrine was simply built from scraps of wood and card. And the bamboo sticks came from a bamboo kitchen place mat.
I'll touch on the urban terrain in another post; it was created long ago for my collection, but it will certainly find some use with Senjutsu.