hobby knife (or some other sharply pointed instrument)
sculpting tool (you want something at least three times as wide as the knife blade with a blunt edge)
water - remember to keep everything wet!
Mix your green stuff using whatever combination you prefer. You want just enough greenstuff to make a level field across the base you're playing with - if you're using the inset bases try and make the greenstuff level with the bevel otherwise whatever height you want for a normal base. Use your knife to carve off any excess greenstuff you don't need - if you need more simply add more!
Don't worry about the finger prints for now, we'll fix that up later.
Now's the time you start to make your pattern which will eventually become the individual stones. Find a reference picture and work from that though there are two general patterns - organised (i.e. paved street) and disorganised (i.e. more natural looking). I went for a disorganised look based on this:
and that's what the WIP pictures will be based upon! I start by working outside in with some hexagonal like shapes on the edges of the base of differing sizes. Use the tip of your knife (which should be wet!) to make the incisions - you want to lightly drag it whilst moving the knife up and down These cobblestones aren't fully formed because they are on the edge of the base so it's a good place to start and gives you exactly how much space you have left in the middle and helps with the disorganised look.
If you're going for a more organised look or a different shape just change the way you approach it. For example, if you were looking to do an organised rectangular pavement start on one side work your way across and then build the next layer of pavers rather than working around the edge of the base.
Step 3 (if you're doing an organised cobblestone array, skip to Step 4):
Once you've got the outside done you need to fill in the middle - the majority of the joins are going to be close to where other stones have finished so I generally extended the groves made during Step 2. Continue this process until the entire base is divided up.
Now's the time to make the grooves/gaps between the stones more realistic. Having used a knife blade for the initial layout and cutting of the stones, the gaps are very thin and the edges are very sharp - this works if you're doing something like tiles but since we're making a base out of stones we need to widen these gaps and give the stones a less artifical feel (unless that's what you want).
Grab your sculpting tool and using the blunt edge, force each of the gaps wider - wiggle the tool around a bit as well to get some rounding going on with the stones. Do this for every gap and each stone.
This is where we see a lot of greenstuff pushed around as we're forcing more of it out from it's original position. This provides the basis for the 3-D element of the base so shouldn't be worried about too much though if any spills over the rim of the base, clean it up with your knife before moving on.
Now it's time to get a bit of a natural feel to the stones - we've given them some texture with our sculpting tool but for the most part they are still pretty flat and have finger prints all over them! So, time to whip out that stone I told you to get. If you don't have one, go outside (yes outside) and if you don't live in the centre of a big city, a few minutes walking around should find you a suitable candidate. You want one with a lot of ridges so if you can only find smooth ones, take a hammer to it to break it up. Here's what mine looks like (ya, it was painted when I was younger).
What we're going to do with the stone is roll it across the face of the base. This imprints the stone texture into the greenstuff and will leave indents across its surface - i.e. a natural look. You don't want to press too hard but not too lightly either - the former will squish all the work you've done and the latter won't do anything. It's a pretty easy balance to find so don't worry too much and if you do squish the greenstuff a bit, you can always patch it up later.
Make sure you rotate the stone every so often and run it across at different angles and along different parts of the base (particularly big ones) to get an even distribution of the stone's imprint.
This is basically a repeat of Step 4 in case any of the gaps between the stones collapsed whilst you were imparting some texture onto the greenstuff. Just whack the hobby tool in there to spread the stones out again and clean any excess greenstuff spilling over the edge of the base.
You're done! Wait for it to dry (12-24 hours generally depending upon mix), slap an undercoat and away you go! Here's how I painted mine:
- Undercoat black
- Base coat with an off white (Bleached Bone)
- Ink entire base with a dark brown (Bestial Brown)
- Dry-brush with an off white with a tiny bit of white mixed in (Bleached Bone + Skull White)
- Ink only the grooves between stones with a lighter brown (Snakebite Leather)
- Final dry-brush with an off white with more white mixed in (Bleached Bone + Skull White)