This cuvette frame's design notes are here, along with previous versions and other design ideas. It can be used with this procedure

Download and cut out all the five pieces:

all-together-9-8.511.pdf

all-together-9-8.511-2.pdf

I recommend a card stock like a cereal box. lines can be scored with hard presses of a pen, butter knife, or other smooth blunt thing.

Start with the main frame piece and pre-crease the folds:

Slide the long tab through the opposite side wall, and then tuck in place:

The long strip with triangular holes should be folded up like this:

Don't completely fold up this little part, just fold along the length-wise fold:

put it together by putting the M-folded sheet into the box, and sliding the V-folded strip through the center. Make sure the matching rectangular cuts are on the correct side, so that we can slide the laser attenuator in place.

That rectangular cut in the V-folded strip can get caught on the last little push through. watch it.

The last centi meter is the hardest to get through.

once through, push the tabs in place on both sides:

Alright, the frame is almost done! Now to put the cuvette holder in place.

Pre-fold the cuvette holder:

This fold is the trickiest. Push inwards on the center section while folding. It will pop in place. Crease all the way flat:

Now lets put it in the frame:

fold the bottom flap up and through, and slide the front of the cuvette holder down on it:

Now close up the other end of the frame:

Now assemble the laser attenuator:

Place in front of the spectrometer, add cuvettes and a 405nm laser pointer, and you're done: