Question about the sticky

In the guide above, there seems to be some info missing from the section on making the waterblock. It goes from being a raw copper bar to being a finished waterblock in 2 pictures, lol. How do you rout the bottom of the thick copper block to allow for flow? What tool did you use and did you use some sort of baffling pattern? Really very informative post, thanks for taking the time to put it together :-D