I was successful in creating Peter Beck's Christmas Tree ornament.

The project requires 50 modules, not 120. There are 30 outside modules and
20 inside connecting modules. The outside modules correspond to th edges of
a dodecahedron. The inside modules create an interior icosahedron.

I used 3M Post-It notes cut in half, each starting rectangle being 3" by 1-
1/2". I folded the adhesive to the inside on the first step, so the
adhesive was not holding the project together. It probably would have been
possible to use the adhesive to keep each module together. This would have
required a lot of extra care in the assembly, but produced a much sturdier
product. As it was, once I got the hang of it, I didn't have any major
problems with modules coming apart. The finished construction required no
staples or extra glue.

A previous attempt using 1" x 2" rectangles cut out of graph paper kept
falling apart. I've got a partially finished ornament made with dollar
bills, which seem to work fine.

The ideal shape for an outside module is not an equilateral triangle, but an
isosceles one with an apex angle of about 42 degrees. I took care of this
by allowing the outside surfaces to bow outward.

To finish the assembly I left three outside modules and their common
connecting module until last. The outside modules were threaded into place
but not closed, with the ends of the paper pointing outward. The connecting
module was placed over the nearest ends of the three outside modules, then
the outside modules could be closed.