Hi,
I haven't found a tidy way of doing this. Rene suggested plastic soap cases which would probably work for single interfaces, but where you have multiple interfaces (I have 4) finding something that is compact and can mount the boards whilst catering for the cables at both ends is tricky. I ended up putting insulation material between the boards and putting them in a plastic kit box with cable ties to keep them together. Not elegant, but works!
Ideally, you want something that can clamp or hold the sides of the boards whilst allowing visibility of the green LED. The edges don't have a lot to hold on to so maybe some firm non-conductive foam grip arrangement might be the way.
Cheers
...Steve