This is your basic slip knot, I used a phone charger cord, because that was the only thing on hand.
Step 1: Basic Overhand
Just like the title says, do a basic overhand knot.
Over the left.
Back under the left.
Bring it under the right, then twist it around the right rope ONCE.
Then pull it up like the 3rd picture.
Step 3: PULL!!!
Step 4: DONE!
Done! now you have a slip knot!