When you draw your lines, draw them outside of the box just a bit, then having the box line on top, do, Front Minus Back. You have to do it three times, one for each shape. then use the virtual segment delete tool, this is available in 12 and X3. If you have an earlier version, if you draw the shape with the artistic media tool, break them apart, remove the line and then trim each one. Then delete the outline from these three shapes. You have one shape, then make a square for the background and fill it with black and the shape with all the cutouts, white.