The parent should use the box cutter or scissors (whichever works best on your cardboard) to cut a boomerang shape from a large piece of cardboard. An empty cereal box can be used for the cardboard. The boomerang is a V-shape with the V-sides of equal length. It is widest in the middle, and has two rounded edges at the tips of the V.
Let your child decorate the boomerang with markers. She may want to use the Internet to look up Australian images that she could use to decorate her boomerang, for example Australian animals (kangaroo, koala bear, platypus, emu, etc.), the Sydney Opera House, Aboriginal designs, or the Australian flag.
Let her practise throwing the boomerang to see if it spins and returns to her when thrown. You may want to help her cut out boomerangs from cardboard in different shapes and sizes, to test if large or small ones throw and return better.
Some tips for throwing the boomerang are: throw it in a counter-clockwise spin. Throw it in the same way that you throw a Frisbee. Hold one V end of the boomerang, twist your wrist towards your body, and then flick it out to throw the boomerang. Try bending the ends of the V arms down a bit to better the chance of it returning. Or try bending the tips upwards. Everyone has a different throwing style, and the boomerang will not always return, but it usually does spin pretty nicely. Have fun!