Yes. You just crunch up Al foil a few times then smooth it out a bit and fold up the edges to make a little container. Pour in the plaster and let it set! I carved the brick lines into a "sheet" after it had set. To do this I actually used a very small drill bit as a file (normally used for pinning). There are some good tutorials on youtube about using foil to make "rock", the railroad guys have LOTS of terrain tricks. The foil doesn't have the strength to hold much weight, so larger forms tend to flatten out, but for our scale things are pretty OK...
Below is how mine looked before I broke it up.