Summary I used an existing Thingiverse On Air sign from crimsonlion518 and a 9v battery holder from ahmetcemturan to build this On Air LED Flashing sign for Filament Friday. The design was completed in Tinkercad and the electronics were built on a CNC milled circuit board. The electronic circuit is an Astable Multivibrator circuit that creates the back and forth LED flashing without any microcontroller. More info in my YouTube Video: https://youtu.be/ev_GN92xay4 Print Settings Printer: Flashforge Dreamer Rafts: No Supports: No Resolution: 0.3 Infill: 25% Notes: PLA Post-Printing Electronic board was Double Sided foam taped in place. Switch was screwed into top of box. Battery fit nicely in socket.