I've modded a 3x1x6 bin to have an open front with a slot for a microscope slide. Advantages over Zack's: 1) it is a single part, 2) the microscope slide fits tightly enough that it doesn't require glue. Disadvantage over Zack's: 1) it requires supports. It's a mod from kennetek's OpenSCAD bins, and I've submitted a PR to them.