Lets Build a Castle out of Builders Foam

So now that you've decided on the type of stone your castle will be built of, take a look at the stonework: are the stones large or is there a combination of large & small? Granite wears less; sandstone erodes more and so will show up as very weathered.
Because I decided my castle would be sandstone, I've needed to carve each stone individually rather than just scoring the edges. Each of my walls takes approximately 5 - 6 hours to carve ...very time consuming but hopefully worth the effort! I also wrote down the stone course heights to make it easier when doing the next wall; my courses as well as each stone is irregular.
If you're doing granite, you could simply score the edges with a knife and then deepen them using a small piece of sandpaper or an emery board/nail file.

Make sure to keep the knife edge sharp to avoid pulling out foam chips. (If you look closely at my photo, you'll see that this is a case of "do as I say, not as I do".)

If you want to show quoins or crenellation, decide this before starting to carve. My walls have both; I am adding both to the walls rather than showing them carved in relief.

Gemma asked about translations. I've added a translator on the side bar of my blog although you shouldn't need it. Whether you read blogs in a reader or individually, google if set up right, should automatically translate for you. Let me know if this helps, Gemma.