Just attach the headboard to the wall at top. I did a covered headboard and attached to wall and couldn't see the screws. As high as yours will be, it will not be noticeable. Don't just count on bed holding it in place.

Absolutely agree attach the headboard to the wall. Then the bed to the headboard. I made a bed a few months ago, since you are DIYing it you can adjust it as need. Maybe building the headboard to attach to a 2x2 or 2x4 (depending on the depth you want the headboard to have) frame attached to the wall???

Here is the one I built a couple months ago...


Best,
Renae
www.knowtheit.com/blog

I've been planning on trying to do a diy headboard. Don't know if you already have a design in mind but here are a few. You can do these in individual pieces which makes building and hanging much easier.