I made a paper pattern of the back of the fireplace. Then I rolled out scrap polymer clay, making sure the sheet was larger than my pattern, and used one of the impress molds I bought from Malcolm's Miniatures (via the Dutch dolls' house store Silly Sisters). I have quite a collection of these, now -- the one I picked was the Tudor brick -- these are longer and thinner than later bricks, and I thought it would give a nice detailed texture for the back of the big fireplace. English bond would have been okay, too.
My impressing is so very far from perfect, I almost crumbled it up and rerolled it, but I think after it's been painted and the fireplace has been filled with stuff, no one will notice my lousy work!
Then I baked the impressed sheet. It baked a little wiggly in the oven, as it tends to -- I find that if I glue it down really well, everything comes out okay. If you want to cut down on the wiggliness, then make your sheet of clay thicker and use more even pressure when impressing than I have here.
I cut it to shape using scissors (one of the wonderful things about impressing bricks into very thin sheets of polymer clay is that it's a cinch to trim).
Here it is, back in the fireplace, after it's been painted grey and then had its first dry brushings with cadmium red, raw sienna, burnt sienna and burnt umber. It now needs the detail work to bring out the grout, blacken the central bricks and so forth. In terms of sheer speediness, this technique is really great!
Does anyone else find that taking photos reveals all sorts of things that the naked eye can miss? Looking at the photo below, I see that because the "brickwork" doesn't fit the fireplace cut out perfectly, I'd best paint the edges of the back of the fireplace in a nice bricky colour to help camoflage that :)