Ok. I apologise for the lack of work in progress shots. I did this a while ago and have no idea where the pics would be or if I even took any.
I bashed this out well over a year ago now and it's done a few road trips to Infinity tournos, so it's a bit worse for wear but this is the "one week" modular 6x4. Construction went like this. I'll talk about everything that went wrong and what I would do differently at the end.
1) Start with 6x 2'x2' blocks of chipboard. I used 10mm or 12mm. I forget which. Doesn't matter. Wouldn't use it again. See post mortem for why.
2) Rough out a design for the board on some paper. In my case, I went with four boards having one corner each as elevated and two boards have two sides with dips in them. Its pretty standard modular design. Allows for one large elevation, two smaller ones or four corner pieces on a 4'x4' and a 'river/gully' section on a 6'x4'.
3) Using your design as a guideline, figure out how high you want your hill to be. Then start cutting out strips of 6mm mdf 2 feet long. In my case, I needed eight pieces that were 4" high and 20 that were 2" high. The 2" height ones are the "standard" edges, save four that had a matching recess cut in them for the "river/gully".
4) Take one of the high pieces and make your template for your hill. Cut out the shape, then use it to mark and cut the remaining seven 'hill' pieces the same way. As long as at least one corner comes down to the 2" height of the standard edges and all the hills have the same shape, you're fine. This won't result in a perfectly circular hill though as we can stretch and warp the hill out in to the board.
5) Fix the edges to the bases. Glue and wood screws will do fine. After the thing is filled with polystyrene and glue, nothing will move it. Make sure to pilot drill the chipboard before putting screws in it or you will blow it out.
Thus ends Day 1. At this point, leave it for the glue to dry.
6) Using whatever polystyrene pieces you have lying around, fill in the board. When you get to the edges, deliberately bring the polystyrene up past the wood and just use a knife or plasterboard saw to cut it back down to shape. It doesn't matter how rough the polystyrene edge is. In my case, I wanted a rolling field, so I used a lot of flat sheets cut to shape, which gave me a nice flat result. Then I just stacked them up for the hills. Use a fair bit of glue to hold everything in place but don't worry about filling in the little gaps too much. That comes next.
Stop Day 2 here and wait for the glue to dry.
7) Now that everything is in place, grab a wallboard/plasterboard saw and some sandpaper and start sculpting. As long as your foam meets your wooden edge, it will look fine, so go nuts making wierd shapes or smoothing down your hills. I staggered everything to stop models getting broken but you can go nuts. It was at this point, before filling, that I grabbed the pine bark chips that make up the rock face and glued them in.
At this stage, go to Bunnings and grab a bucket of PolyFilla. You'll want a large bucket. This is how you're going to smooth everything out and get a nice level coat. Smear it all over the joint. Fill gaps around the edges and up and down the hill sections. Don't stress about texture. That comes next.
Stop Day 3 here. Give the Filla overnight to skin and set. Sand it down before you start the next step.
9a) At this point, you have two choices. If you're flocking with grass, I recommend doing a first pass of texture, then painting. Use a bit of PVA and pick out any sections you want to look different to the bulk. In my case, it was sections of exposed dirt/sand. If you didn't care about this, you can skip it and go straight to paint. This colour will depend on what you want your final result to be. I went with a dark, loamy colour. Or you can go crazy, flock the whole thing with dirt, then flock it with grass later. But that's just double handling.
9b) If you're just flocking with dirt for a desert/ice board, then you can coat the whole board in sand/texture.
Stop Day 4 here. Wait for either the paint or glue to dry.
10a) At this stage, if you haven't flocked, then flock the whole thing. I used Woodland Scenics tubs. Don't worry about how boring the grass looks. We fix that. If you're the sort of lunatic that likes to break things up, then you super glue tufts on in random places at this stage as well.
10b) If you already flocked, then paint.
Stop Day 5 here. Wait some more. If you're super impatient and an early riser and insomniac (and the days are hot enough), you can probably mash a few days together here. I had a week off and nothing better to do when I did this, so I don't think it actually took me this long.
11) At this point, we're detailing. Any rock sections, hit with black paint. Grass sections get drybrushed. Start with Goblin Green or equivalent, then work up to Yellow. Hot tip, don't use GW paints. Go to Bunnings. Buy small testor pots of house paint. And use a gigantic brush. Make sure you're pretty light on the paint before you start so you don't smear the grass too much but otherwise, go bonkers. Light strokes. At this point, your grass will start to improve dramatically. If you just textured your board with dirt, you can start drybrushing up to whatever you want. When the rocks dry, same thing. Drybrush up in grey. Pine bark is incredibly textured and looks amazing like that, so don't be shy.
Congratulations! At this point, you've got a playable board. Well, you don't have any terrain. But the board looks pretty. I did start some terrain at the same time but didn't finish the bulk of it.
What would I have done differently?
: The chipboard base makes it surprisingly heavy. Still able to be carried one handed for it's size but unwieldy. If I did this again, I would start with a thinner base and build a lighter frame. 6mm mdf for base and sides and 20-30mm thick square beams to fasten to.
: This was more because of how I approached it but I would use expanding foam over polystyrene sheets. The outer shape is already there and this would give me an easier way to cut in rivers, craters etc. Expanding foam cuts beautifully with a retracting knife. Polystyrene less so. This would also have cut down on the amount of glue but curing time would be similar and carving time would add on more, so it would probably just be a wash.
: Those of you with eagle eyes would notice that I started with 2'x2' boards, then screwed 6mm on to the edge of them. It's not a huge difference but does increase the size of the board. It also made some of the boards a slightly odd shape. Corners don't line up perfectly. So start with the base, then find a way to butt them up on top, not to the side.
: Grass fields are boring. This method would have worked fine for pretty much anything but an urban board and given a second pass, I'd probably do something a bit more exotic.
What went right?
: The board was designed for Warmachine and Infinity, so it had a few things to take in to consideration. I needed large flat areas to pile scatter terrain on but in the event that I was light on terrain, I wanted elevation changes across the board to help block LOS. That's why the hill sections drop down to a valley before coming back to normal height and in practice, it works perfectly. Same for the design. I actively avoided chopping huge holes or craters in because I was planning on making any features like that scatter terrain rather than fixing them in place. This allows the board a huge freedom in the way it's arranged. This is the set up for a standard Infinity game.