This is a simple method of a rock face that I made as a test piece before starting work on a larger diorama.
Step 1: Materials
For this I used the foam packing bits, PVA glue and a piece of wood.
Using a craft knife, cut the foam pieces lengthwise and roughly place on the piece of wood and make sure you have enough to cover the whole board.
Step 2: Attaching the Foam to the Board
Using PVA glue, attach the pieces
Don't worry if there are some spaces, you can cut some more foam to fit the spaces, or leave them to look like deeper recesses in the rock face.
And then leave the glue to dry
Step 3: Shaping
Using a hot soldering iron, gently tap and pass the iron over the foam to melt and create the rough surface.
Don't worry if it doesn't look like much at this point.... it will take shape.
Step 4: Painting
Now undercoat the whole thing.
I used red as I wanted to make this look like a lava path (as I said, this is only a test piece)
If going for a rock face, then a black undercoat then blues and greys are the colours that I used.
In this case, I used red as the undercoat then dry brushed yellow over the top.
Keep on with the dry brushing until you are happy with the result
At this point, I then dry brushed black on some of the raised areas
You can then varnish using a matt varnish and the admire your handy work.
I put the rock face next to a test piece of muddy path that I made.
I like the overall look of it... and I hope you do too :)