Browsing through Pinterest I found the perfect headboard design which fits to my previously built bed. I stumbled across various design iterations of a headboard [1] sold by IKEA in Japan.

It's pretty straight forward to built, so I gave it a try. I wanted it to be as clean as possible, no screws visible and flying of the ground. I think it turned out quite well for a cheap and no professional tools built. Sure it has some beauty marks, bent planks and it is not as sturdy as it's not attached to the wall. Nevertheless, I'm happy about the upgrade. All in all I've just spend roughly 60-70 Euros for the wood and screws.

[1] https://www.ikea.com/jp/en/p/mandal-headboard-birch-white-50176313/