I love clay shingle roofs, they're easily my favorite material to make a roof with. I do find that making them in any real amount to be really tedious, though, considering how many you need to make a sizeable number of roofing blocks.
Similar to how bricks are made with just four pieces of clay in the crafting grid, maybe they could be made in a similar way? For example, two pieces of clay arranged vertically to make a shingle.