Icosahedron
The icosahedron is a 20 sided polyhedron made of equilateral triangles. This makes it a relatively easy solid to fabricate. The hardest part of fabricating a form like this is keeping everything consistent. With the help of digital fabrication, jigs and fixtures can be created to help easily make clean cuts and keep everything joined at the correct angle. Below are files to help

Rhino and Grasshopper File
Below is a link to the Rhino and grasshopper files to generate your own jigs. In the Rhino file you can scale the icosahedron to your desired size. Be sure to the form and the metal parts together. Within the grasshopper file you can modify the material thickness, kerf tolerance, number of joints and number of sections. This file can also be modified to accommodate different polyhedron.