How can I make this model?
Without any restrictions to your methodology, your objective is easily accomplished. Thingiverse has a truncated icosahedron model available for download and printing.



Because the creator has included in the download the OpenSCAD source files, you could edit it to meet your bed limitations. I've downloaded the source, opened it and found the model is a single hexagon, until you change a parameter from 6 to 5 to get a pentagon. I suspect the assembly is up to the builder to figure out.

It appears that the default is for a 50 mm diameter sphere. Change the 50 in the code to 300 or so to reach your 12" desired diameter.

An alternative to friction welding would be just about any decent epoxy or even a 3D printing pen such as the 3Doodler.