Things you will require
1) Buttons from broken toy pianos/guitars. I had mine from a guitar, and were in shape of animals faces and stars.
2) Neodymium magnets, these are strong magnets, and available on Amazon. I had mine lying around, they are 7 mm in diameter and 2 mm thick. Make sure you understand the steps, and buy the ones that will fit.
3) A hot glue gun
4) A dremel or a knife to scrape away unnecessary plastic.
5) A sand paper.
Note of Caution:
Neodymium magnets are very powerful, and can pinch skin if not careful. Always slide magnets, and never try to hold two magnets close enough that they can attract each other. The ones i had were strong enough to have a substantial pulling force at 1.5 inches.
Turn over the button shapes and see, if any plastic need be removed. We have to ensure that the button stay flat on a surface.
Pour the hot glue in small quantities, the plastic can disfigure if a lot of it is poured together.
When enough levels have been filled out, place the magnet so that it is flush with the border of the face (See photo!)
When the hot glue solidifies, go ahead and use it to you to do notes and grocery list on the fridge.