I use a hand drill & a Flex Shaft drill (think of a dentist drill on steroids, big 120v AC .5A motor that spins at 14,000 RPM) for my blocks.
Right now I'm working on a "pitted" block for my GPU which simply has rows & rows of overlapping drill holes to create turbulence. It almost looks like someone has chewed on it with their molars

. I follow the school of thought that a thin base means you can get heat to the water faster & it wont "insulate" the heat so much. The thicker base school of thought is valid too, the designs end up being different often times. I figure with a GPU like my RV350, thinner is a good thing. Perhaps it isn't but I'll find out by building blocks now wont I. Good luck with your design.