Added: You can now go see part 2 here.
When I am setting up an encounter where I use terrain, I find it easiest if I set up the whole board then move rooms over to the table as players explore them. This keeps all the pieces close together, even if I remove some or hide pieces for later reveals. I typically have used foamcore or xps (the pink foam) sheets to hold everything so I can pick up the whole board to move it all at once.
Blank white or pink boards are boring and unhelpful for immersion. They also are not useful by themselves as a background so I am taking a page from wargaming’s book. I am building a terrain board with texture and color.
-Two cheap foamcore sheets (dollar store foamcore is easy to remove the paper)
-A thicker foamcore sheet
-Various grades of sand, tiny gravel, construction sand, and grass flocking.
The first step I forgot to take pictures of, but I removed the paper from both sides of two sheets of dollar store foam core. Then I glued one to each side of a thicker piece of foamcore. The thick foamcore still has its paper and I glued both sides at the same time to prevent it warping in one direction as well as weighing it down with lots of books on a flat surface.
This leaves a rough edge as the foamcore sheets are not exactly the same size, so I glued strips of paper around the outside and used a boxcutter to cut away areas with too large a gap of overhang.
The third step is to texture the foamcore on each side. I am aiming for one side to be a grassy/outdoor battleboard while the reverse side is a stone cavern. I am using a ball surrounded in aluminum foil for the first pass of texturing. Rolling it around, slamming it into the foamcore, and occasionally scraping it around, I got a random texture that I liked. Then, a boxcutter was used to rip out some areas that will later become puddles.
Next I added some areas of cobblestones to mix up the cavern side by drawing them in with a wide ballpoint pen. I left the edges of the outside bricks open so that when I glue on sand, it will look like the rock/gravel/sand is covering up a larger area of cobblestone.
Next, I covered the cavern side with watered-down glue, roughly a 50-50 mix of glue to water for easier coverage. I used a variety of different sized sands and tiny rocks, plus a few areas of green flocking, to create a varied cavern texture. I found that taking a handful of sand and shaking/sprinkling it over an area gave a random distribution better than trying to pour it out.
I gave it a day to dry and then brushed on another coat of watered-down glue to harden everything up. I also added a bit of sand and flocking to a few areas that were light, especially around the edges where there were some gaps between the board and the edge-banding.
After another day of drying, I flipped it over to the grass/outdoor side and gave that a coat of watery-glue. Then a generous covering of sand and lots of grass flocking in yellow-green and green were added.
I worried for a bit, thinking that I should have painted the foam a dirt brown before flocking, as it was very light with the white underneath. I would probably suggest that as the right route for someone else doing this. However, if you did add your flocking first, no worries, as a second coat of watery-glue and coating the board with more flocking (including the flocking that shakes off after it dried the first time) gave it a solid yellow-green coloring.
In part 2, I plan to liven things up more with paint and water effects then toughen up the whole thing to stand up to serious play. Stay tuned.