The wiring is pretty straightforward. the toggle switch is hotwired to the permanently hot side of the mosfet/relay. when switched on it outputs power to the signal pin on the relay, which allows current through to the power delivery unit.
Melt in the thread-certs. Route the wires through the base and glue in the spade connectors so the connect with the batteries' outer "pins". *Note the beautiful super glue activator stains.
Screw the halves together and if wired correctly, it should work.
The author remixed this model.
I used this base as a starting point.