Print bottom and top. Print flame top with %1 fill and 3 shells. Once done drill a hole in the flame top bottom for a LED. Then hot glue the flame top to the light top box (make sure to align the holes).

I programed an Attiny 85 with an Arduino board and used a CR2330 flat cell battery for power 3V 250mA. The circuit board has the 8 pin chip, one 10k resistor, one LED and power wires. You'll need an Arduino UNO or equiv.

To program the Attiny 85 chip with an Arduino UNO go here:

hlt.media.mit.edu/?p=1706

You can Google search for the Attiny 85 and Arduino Uno to get a good price. Lots of them out there.

The Arduino sketch I used to make the light flicker is:

===================================================================
// LED Fire Effect
int ledPin1 = 0;

void setup()
{
pinMode(ledPin1, OUTPUT);
}

void loop()
{
analogWrite(ledPin1, random(255));
delay(random(100));
}
======================================================================

Once the Attiny is programmed with the above sketch, then you're ready to glue the small board into the top case with the LED pushed through to the tip of the pyramid (since it's hollow). You can add the battery and possibly a switch to turn it on and off. Right now I just remove the battery when not in use. The bottom plate can easily pluck open and press back together.

Here's a video of it flickering:

youtu.be/-C1LpVAJSZk