King Size Bed Support...

I reviewed the forum and couldn't find a post regarding my specific question, so I apologize if I am being repetitive. I am near the end of my build of the Farmhouse Bed in a King. As many, I am wondering as to how would be the best way to build the supports for mattress and box springs. I too do not want the box spring to ride to high. My question is has anyone mounted the side rails to the legs, and then mounted 2x4's with joist brackets similar to what is used to build floor joists for a home or patio? It seems to me it would be cheap, easy and easily support the weight, but I don't know if there is a reason this wouldn't work, if someone has already tried this before. 

Forums