Mona Sans VF is exported from the Glyphs interface directly into the /fonts directory. This is the easiest way to distribute multiple cuts of the variable font.

1. Open MonaSans.glyphs project in Glyphs.app
2. Use File > Export > Variable Font
3. Save the exported variable font into the /fonts directory.

Running build.sh will try to move them to the right place, if you don't put them there already.

The build.sh script handles building font files that meet Google Fonts specifications and requirements, and builds into the /googlefonts folder. It also checks to make sure the other fonts are in the right place.

sh sources/build.sh

You'll need gftools and ttfautohint installed. Which you can do via:

pip3 install gftools
brew install ttfautohint