4- Now that you did the 3D, you now want to add some type of style in it.
Below i did a style called GRIDS.
on each side of a 3D box. Ink in a phat downward line, then a meium one, then a thin one. Repeat inside every 3D box on both sides of each box (unless there is no space for it, you can also use only two grid lines if thats all that fits.