This block isn't technically difficult (the only new thing is a partial seam) but relies heavily on accuracy. The half square triangles are very small, and the whole thing won't fit together unless you cut carefully and have a consistent quarter inch seam.
I suggest you use three colours, a dark, medium and a light. Although the block finishes at 15" you only need a half yard of background fabric (light), a fat quarter of medium and a fat eighth of dark.
