Here is an easy one!
Pick up a used one and refurbish it. That’s the easiest way. No saws, no drills, no sheets of plywood.
They can be painted, be “upholstered” and even have contact paper put on them.
You can hang something on the wall where a headboard would be. I did a large cotton bloom wreath in the center of the bed with cathedral style frames on each side in the master.
Here’s an easy one we did: https://www.frugalfamilytimes.com/2019/10/green-reclaimed-headboard-diy.html?
We used a vintage wood & glass door