As the title said, this is very simple. all you need is paper and fingers. Letter sized will do.
Step 2: Folding
First, fold it in half(First image). Make sure the bottom flap is sticking out a bit like in image 2. Now, flip the paper over, and fold it in half again (image 3). Your done!
Step 3: Holding
This my sound complicated, but its not. Hold the inner 2 flaps together, like in image 1. Then, pull those flaps up, and pin them with the outer 2 flaps. Check out what it should look like in picture 2. NOTE: Make sure the when your pinning the inner flaps, they are not stuck inbetween your fingers.
Step 4: Poping it.
Throw it down, but dont let go. This vid will give you an idea: