These models divide the small (red) Eurobox inserts into halves or quarters, this allows for more efficient storage of small parts. You need to import the STEP or STL files into your slicer and print them with 0 top layers, 0% infill and 1 or 2 perimeters. Pay attention to the bottom side to orientate the prints. 

The model doesn't fill the entire space because of the organizer boxes: the lid has notches to keep every insert into place.