There’s no specific trick to getting blocky shapes, I use a variety of tools and and often check my angles to make sure I have the right orientation.
Usually I start off by figuring out exactly what feature I want to exagurate and gradually start pushing it off the head, sometimes using a mask. Usually it’s pretty puffy so you use smaller brushes to start building up peaks on the feature. It’s also important to subtract areas to make some kind of seperation from the rest of the face.
Once I have it massed out I use the flatten brush with a square shaped alpha, just carefully run it over the areas you want flattened, if it’s being difficult, drop the intensity down to 2/3rds and work at it more gradually. The last little bit is just some simple strokes with the pinch tool. It’s important that the pinching comes last since it tends to pull your mesh in certain areas and it screws up the cavity shading a bit.