If I had to, I'd use a tenon saw (sharpened rip) and a rebate plane for what are, in effect, large rebates.
I'd saw out a cuboid lump to make the really big rebate on the lower side, then clean up with the plane.
For the smaller rebates at the top, I might plough down with a narrow cutter one way, then plane the rest away.
The oblique angle outside on the right can just be planed with a jack plane.
I'm assuming your photo is the length required, not just a short sample.
But to answer your question with another question, why do you want it made from solid? That seems very wasteful of wood and effort, compared to what you have already done.