Hi, I´m making a square cake for a birthday party and i have to cover ir with black and white fondant, in like big squares one on top of another. I cant decide if it would be better to just cover the cake in white and then put a big black square and then a white one and so on, or if i should cut it, roll it together and then cover the cake. I need help!

If you roll them together you will lose some of the sharpness of the squares.  Not sure what you mean by on top of each other?  If you mean staggered you could cut the squares so they fit together like puzzle pieces so they sit flatter.