These are the things we need: a silver varnish pen or some sort of conductive paint, four LEDs (LBT 676), and four resistors of 130 ohms.
Starting with painting the wires from the batteries to the magnets and through the little holes we drilled before.
I used some grey stuff to figure out where the shield ends on the base.
I superglued all the electronic components on the base, keeping an eye on the polarity of the LEDs.
I tested each LED before the final wiring.
After the paint dried, I started the first tests. Looks fine so far.