Step 1: You will need...
Some PVA glue
Half a ping-pong (table tannis) ball
Some scissors (preferably small ones)
Some thin card with the template printed on
And a marble that fits inside the ping-pong ball.
Step 2: Cutting...
You will end up with two, pritty much identical circles.
Step 3: More cutting...
Cut two of the lines that are going in towards the center of the circle. Cut two that are next to each other.
You can now fold down this 'tab' that you have created. This will help keep the circles from moving in relation to each other.
Finally, cut the rest of the straight lines.
Step 4: Shaping...
Push the card into the ping-pong ball and smooth it out with your fingers.
Use the marble to help achieve the hemisphere shape.
Remove the card and do the same with the other template.
Step 5: Glueing!
Now draw lines from the centre to the edge of the template with glue. Do this on each 'tab'.