I’ve done a little different. I don’t know if easier… But it looks ok.
First I’ve created the central cube. Then I duplicate it to make the top edge. Finally I duplicate linked the top cube and move it to the bottom.
In the edit mode, using the link I’ve created the wedge by moving the cube edge together with its opposite and removing doubles to join them.
Back in edit mode I’ve rotated the bottom edge and then join the three together…
Then I’ve moved the origin to the bottom edge and put it at 0,0,0