The long rails, to connect the two pairs of legs, don't need to be so thick. And because my wallnut boards are 5cm thick, there is enough material to cut two boards from one. But this is a resaw operation, the worst case scenario of cutting a board, in the length, through the depth of the board.
First sharpen the saw. With a triangular file in my makeshift sawvise, which works perfectly btw. I didn't reset the teeth, there still was enough set left after this quick sharpening.
I layed out the marking lines on both sides. And then there was nothing else to do, but sawing. Because it is very easy to saw out of plump, I first estabilish a groove on one side, flip the board over and do the same at the other side. And then remove the material in between.
I didn't time my self. I guess net sawing time was less then an hour. I took a long teabreak in between. But everything went smoother then expected before hand. And I managed to cut pretty straight too!
And then there were two: