The circuit shown uses 5 components and is easy to build.
How does a relay blinker work?
When the circuit is turned on, the LED lights up and the capacitor begins to charge. When the voltage on the capacitor is high enough, the relay pulls the clamp to the NO position (normal open / normal open); during this time the capacitor is discharged and the LED is off. Basically, the voltage starts to drop on the relay coil, at which point the relay terminal switches to the NC state (normal close / normal closed). The process is repeated until SW1 is brought to the OFF state.
The assembly can be powered between 5 and 7V from a direct current source.
List of required components:
1 x Breadboard test board + connecting wires
1 x C1 = 2200uF
1 x K1 = 5V relay
1 x LED
1 x R1 = 470 Ohms
1 x SW1 (switch)
1 x Terminal contact
For a better understanding of the circuit's functionality and to make this assembly on the breadboard we will need the electronic diagram presented below:

To better understand how this project works, we have attached the video below:
Download the manual and the electronic diagram
To carry out this project in your own laboratory, download the manual here and electronic schema in .dsn format (TinyCAD design) by here.