What you will need:
-Capacitor(Different values will change the flashing speed)
-Resistors ( 1x10kΩ , 2x1kΩ )
-9v Battery Clip
Step 1: First Components
Then, add two of the resistors, one of them 1k and the other 10k.
Step 2: And More Components
Changing the capacitor with other capacitors will change the blinking speed of the LED- So that is why I didn't specify one capacitor.
Also- large capacitors seem exciting... but it just makes your LED blink very very slowley.
Step 3: Final Components
Then well add a small jumper connecting gnd of the capacitor to the gnd rail. Thats it- so you can connect a 9v Battery to it and you'll see the LED start to blink. If it is really slowly blinking, replace the Cap with a smaller Cap. If it is blinking to fast, replace the Cap with a slightly larger one. (I used 100uF)