"Yeah, Justin's method is what I use, too.
Always start with the mattress size and make sure you design in room to actually be able to get the sheets on the bed once it is built.
If you are using a flat surface for the mattress then this…"
"From the beds that I have built, I measure the mattress and work from there. That will give you your interior dimensions of the frame. Rockler sells non-mortise bed rail hardware that makes things easier too."
I have built many kitchens and finally decided to buy the Foreman, because my latest kitchen consisted of 28 cabinets and I was over my hand hurting from all the drilling, moving the clamp etc., it seemed like a smart choice.