It was really easy – all you need is clay (I used this) and some small magnets (I used these), as well as some strong glue. I shaped small clouds out of the clay, dried them in the oven (read the instructions on the package) and glued the magnets onto the backs. Done!
Now they live on the fridge next to our Copenhagen streetmap jigsaw puzzle. I probably haven’t used clay since I used to play with salt dough and play-doh as a child, but I’m definitely doing this again!