Yesterday, I saw this picture on a forum
My first try was far from perfect, but now I think I have understood how to model it.
It took me several hours to figure out how to proceed, but it is less than 3 minutes when you know what to do. As the original poster wrote, I enjoyed the challenge and learned a few things 
before having the neat final result with the clean fillets and the nice transition between the horizontal and the vertical flange.
