
Heck, old gauze bandages would work fine.
Natural fibers or a very loose weave make this easier.
Buy some absurdly cheap fabric from the fabric store (We had some old $1 a yard cotton muslin lying around) and cut it into strips. So you can go buy plaster cloth at the hobby store or you just make it. When I was done with my lattice-work, I clipped the corners of the posterboard on the sides to round them off. It's as simple as 1) crumple up a sheet, 2) stick the wad on the terrain, 3) stack it higher, 4) if it gets unstable use a piece of tape to hold it temporarily, 5) when you're done make a "net" of masking tape over the entire paperwad "mountain" (you can see some of the red posterboard backdrop at the edges of the tape). Then I used wads of crumpled up newsprint and masking tape to make a kind of netting of "filled" tape (or rather say fluffed, inflated with, puffed, etc.). It's black here because this is after the primer step. I just made a backdrop of some posterboard all across the back and up the sides up equal to where the forward leading edge of the "wings." I had some junk red posterboard lying around. The backdrop is pretty simple to figure out from the "after" picture below.
I folded the triangular "wings" to form a 45 and 90 degree panel. Then I taped the gate to the foundation, no glue, no pins, nothing fancy, just packing tape.
#PLASTER CLOTH PLUS#
The "fortress gate" was created by measuring out a rectangle big enough for a land raider plus a bit of extra space, then adding two triangles which I then score the backside and folded in. I could have used plywood or MDF or anything else, I had foamcore on hand which is why I used it. It starts with a 2 foot x 1 foot piece of foamcore. However I did take a couple at the early stages.
I didn't take anywhere near as many photos as I should have of my backdrop as I was working on it.