First decorate the box. You can download our Shelley shell pattern or create your own design and paint it on. Cover the box so it looks nice and neat, and if you want to keep the mechanism visible, make sure you don't cover the front.
On the side of the box, find the centre point by drawing a cross with a ruler. You can rub the lines out afterwards. Use a wooden skewer to pierce a hole where the lines meet in the middle. Do this on both sides, so you have a hole in each side.
Grab a grown-up to help with this bit if you need!
Find the centre point on the top of the box and pierce a hole like before. This time make this hole slightly bigger, then insert a 4cm piece of the straw and glue securely into place.
Now it's time to make the mechanism! Cut the two wooden skewers – one to the length of the box and one just slightly shorter.
TOP TIP: Keep the pointy tip as this will help to pierce the cardboard later.
Cut out four circles from some thick corrugated cardboard and stick them together in two pairs, so they're extra thick and secure.
With the shorter skewer, pierce one pair of circles right in the centre and glue the skewer securely into place. Then with the longer skewer, pierce a hole in the second set of circles around 2cm from the edge. Push it all the way through until the circle is in the middle, then glue both sides so it's secure.
Once the skewers and circles are dry and secure, insert the long skewer into the box and then carefully push through the holes on the side of the box, so the circle sits nicely and spins freely in the middle without touching the sides. This might be a bit fiddly so ask an adult to help.
Insert the shorter skewer through the top flap and through the straw. Make sure the shorter skewer circle sits just slightly off centre on top of the other circle.
Test to make sure the mechanism works and then stick down the tabs securely.
Now you can add Shelley's body to the front – get this from the template if you've not downloaded it already. To make the head, tape some newspaper around the top of the skewer, and glue green tissue paper to it. Add some facial features, and you're done!