How can I attach a sleigh bed head board to a wall

I found a very nice head board at a garage sale that I want to mount to the wall. The issue is there is no flat surface on the back of the head board to mount it to the wall. I was thinking I could use some L-shaped brackets to attach it, but I wouldnt be able to do this with the brackets being visible. There'd be no way to hide the brackets behind the head board because I can't reach it once it's in place against the wallMy second idea is to create a flat surface using a 2x4 between the two sides of the head board at the points that stick out the farthest. Then I could use something like a metal french cleat or z-clips to attach it to the wall. The 2x4 would be hidden behind the head board. The head board is very heavy. Probably close to 200 pounds. The z-clips wouldn't be supporting the weight, but hopefully just keeping it from falling forward. The head board has legs that will support the weight.I was hoping that someone has a better idea or has seen how this can be done. I couldn't find anything good online about this. Most people mount a head board with a flat back to the wall