No drawings were used other than sketches on graph paper. I started with the dimensions of a king sized mattress and box spring. Then I measured the foot board with enough height to keep the comforter from falling off when folded. The head board was just designed by eye. Once I got the width, I equally measured out the spaces for the inserts. All of the lumber was based upon stock widths. So the legs were 1 x 6, stiles and rails were 1 x 4's. But the legs were actually doubled in thickness for strength. The rails holding the box spring were 2x6 with 1 1/4 angle. Since we have 2 full box springs instead of one king, I did put a 2 x 6 down the center with legs. but you may not see that in the picture.
Like I said, much of this was built by eye. But start with the King mattress dimensions and you can build out from there.