See this project's OpenSCAD page for information on 3D printing the enclosure. Continue here once the enclosure is printed and ready for assembly.
Assemble the charger enclosure and on/off button as follows:
Solder the on/off button to the EN and GRD pins on the PowerBoost
Plug in the battery and verify that pressing the button toggles the on/off mode of the charger. Then unplug the charger for now.
Use E6000 to adhere the charger board to the two mounting stand offs.
The board should rest with the two mounting holes directly above the two
mounting stand offs.
Also apply some adhesive to the underside of the button to hold it to the button mount area.
Wait for the E6000 to dry before proceeding.
Once the adhesive PowerBoost is dry, plug in the JST from the
battery into the charger. Place the battery in the its slot on the
Use E6000 again to adhere the battery to the enclosure.
That is pretty much it to assembling this battery charger. Enjoy!
Here is an image of the button soldered incorrectly. Don't do it this way!