Simple High Voltage Flyback inverter [without feedback coil]

Step 2 Safety

The high voltage coil is really dangerous. Don't touch the wire, indicated on the picture above.
It will instantly fry your finger.

Even when you are not touching any other wires, electrons will still jump from that wire to your body, so don't think that you're safe when you only touch one wire.

Warning:
When harvesting a flyback transformer from a CRT, make sure the screen itself is discharged before touching anything.
The screen exists of insulating, glass layers, and conducting layers which look a lot like a huge capacitor.

After discharging the screen, it has a weird feature to slowly build up voltages again which were stored inside the screen itself.
This means that after a while, the screen becomes dangerous again. These charges can go back up to 5kV!

To discharge the CRT:
To discharge the CRT screen you should make a connection between the suction cap (this is where the HV wire of your flyback transformer goes to). and the carbon layer which goes all around the screen.
It's best to use a screwdriver to get underneath the suction cap.
You should hear a 'pop' when it discharges.