Creating a level of rectangles without overlap

Hi all, what I have is a very specific issue - I only hope one of you can come up with a better method than I - been racking my brain on this for a week.

I have made a platform game in Orthographic Unity 2D using sprites. The terrain is made exclusively from black rectangles which are put together to form the world. The intro to each level shows it in the distance at a lower Alpha, getting bigger and darker as it approaches the camera. This works well until I have to make the levels. Because of the alpha, any overlapping objects results in darker spots (where the two faded objects create a less faded one) and this looks ugly. I can use drag & V to snap objects to corners, but because I can't scale and snap to place, it is almost impossible to make something to fit a gap. I have to work from one object and line everything up.

Ideally I would have free creative control to drag, drop and design.

Someone suggested making the object light grey and fade them to black (instead of dealing with Alpha) but I couldn't find a way to do this with sprites.

Any suggestions? Thanks.