A crease pattern that results in this tessellation by Joel Cooper. not sure if it's quite the same as how his is structured, but the final visual result will be more or less the same, at least on the "flagstone" side. The funky shape that looks like a big triangle with a diamond wedged into it should twist into a rhombic twist, if I'm not mistaken; the "Y" shape w/ an additional vertical crease in it usually folds into a rhombus twist. YMMV. (I'm not randomly renaming things here but Joel's...
