I'll bet you aren't having too many off cuts going to waste! Just add any bits to the piles of rubble and rubbish.
You'd be surprised James at how much polystyrene ended up in the bin last week..and the worst bit is that my kids track it in the house. Half my work time is cleaning and hoovering..but happy wife happy life and all that.
Anyway...getting bored with matchsticks and corrugated paper..I wanted to try to do some wicker trench revetments like these:

Now I tried to overcome my hatred of getting 'goop' on my camera by doing some basic step by steps. I'm pretty sure this sort of technique has been posted here before but can't remember.
Step 1 is to drill holes about 1 - 1.5cm apart in roughly a straight line. I never measure as I think the final product can look a bit too perfect.

The holes should be the same diameter or just slightly bigger than the heavy gauge wire you use. The two end holes I used wooded barbeque sticks as they don't bend and you can put a bit of force into them to keep the whole thing tight.
Next, get your light gauge wire (I used 0.9mm) and twist off a few times at one end then start threading through the verticals. Do not cut the wire when you reach the wooden ends, just wrap it around tightly. If it seems to be starting to 'lift', poke it down and give it a few turns before starting the next run.

I think I did about 15-20 runs to get my effect.

I did a rough pre-measure on mine so I knew where they were going to go. The beauty of the system is that the whole unit bends to fit the trench shape. Before you pull the whole unit out of the holes in the base board, just turn the thing on its side and give the tops and bottom wires a going over with some superglue. This will stop it slipping off in movement.
Your piece may or may not slide out of the holes easily. On my first attempt half of them had got superglued in (I hadn't turned it on the side). Cut them out if needs be...you can always turn the whole unit over. I left about 1cm of the support wires showing to allow me to push them into the polystyrene for extra support. I used my old faithful ultragrip plasterboard timber stud adhesive to bond them. Looks like mud when you apply it and dries rock hard.Some of it will; squeeze through the wicker..just like the real stuff.


I remember seeing lots of willows while driving around the Somme Valley so the troops probably had a fairly plentiful supply of this sort of stuff along with timbers stripped from the hundreds of shelled villages.
Cheers!