To the make the bunker, I did similar to what I did to make the plaster hill. I decided what I wanted the height to be then covered it in the fence mesh. I probably didn't need to do the insides but I found that the plaster seemed to latch on better than if it was just exposed cardboard
Here's another angle of the same stage. You can see I am just applying the plaster with the plastic putty knife. I did find using the plastic knife a lot better to use than a metal one. You want to flatten the bumps like the one I've made at the top there to smooth it out.
For the roof bit, if you look at the bottom left corner you'll see I stuck a lot of these dowels together, I glued them together first, then put on my screen mesh then added a bit of plaster on the top. Then once it dried I painted it green. I could've added some of that moss stuff to the roof, but I figured I wouldn't bother.
Once I finished applying the plaster I added another dowel to the front as I know I've seen some bunkers with a log there. I painted the logs brown. The inside is a light brown, I'll try to add another picture to show that off. Then the rest is green. For this I could've added that moss to the outside for that foresty feel, but I was happy with how this turned out so I left it as is. Having the removable roof is handy for gaming too.