It is much easier to get a bunch of stuff precisely arranged and uniformly lit when it is lying flat. Especially if you flatten it out by placing a sheet of gla

It is much easier to get a bunch of stuff precisely arranged and uniformly lit when it is lying flat. Especially if you flatten it out by placing a sheet of glass over it. With everything standing up on end you're constantly fighting gravity and air currents, as well as problems like background art painted using water-based media that makes the paper it's on want to wrinkle. Much easier to just squish it all flat with gravity's help.