I like this build, the author basically built a form, and melted the plastic to the form to make a CNC nut. The plus to this is the “nut” is built inside the form vs a 3D printed method where you need to put the nut in afterwards. And you can repeat this process pretty quick to make multiples. Something I might do different is to add nuts to the top (in the pic bottom) bolts instead of straight plastic.
http://www.instructables.com/id/Homemade-CNC-nut-with-thermo-moldable-plastic-encl/?ALLSTEPS