The example was printed in PLA on an Ultimaker 2 at 0.1 mm layer height.

1.  Glue or epoxy a 1/4-20 nut in the recess of the base.

2.  Place screw through top piece and thread the insert onto the screw.

3.  Add a little glue to the insert and use the top piece to push the insert into the base as far as it will go.  Remove the top piece as the glue dries so it does not get stuck.

4. When the glue is dry, thread the parts back together with the screw.

This project was inspired by http://www.thingiverse.com/thing:293679.  I liked the design but I wasn't crazy about the rubber band so I used a thumb screw to hold everything together.