Cut out the cardboard to be roughly around 17cm x 3cm - It can be different from this, just make sure the length you choose is twice the length you ultimately want the finished castanet to turn out! This cardboard piece will be the core of your handmade castanet!
Decorate the cardboard piece with paint, washi tape, markers etc. - anything you like!
Fold your cardboard piece in half and glue the bottle caps on the ends of the inner side
Add goggley eyes on the outside and you're all set!
Bonus:
Put your favorite tunes/songs on and tap to the beat with you handmade castanet!