Take a sheet of A4 paper and fold one corner over to make a
square.
Cut the spare rectangular piece around and around in a spiral,
leaving it joined at the bottom of the kite, to make a tail.
Now fold a side flap to the right as shown. Then fold the small
flap to left as shown.
Do the same folds to the other side. Opened out, it looks like
this...
Cut a piece of strong sewing cotton (button thread) a bit longer
than the width of the kite and tape it to the corners of each flap.
Tie the rest of the reel of thread to the middle. Poke a pencil
through the cotton-reel to make a kite reel that will kite pull
unwind the thread it needs as the wind blows it up.
The kite should fly at about 45 degrees. If it's up too straight it
means the tail is too heavy or too long. If the kite waggles about
too much, try making the tail longer or heavier by putting a paper
clip on it.