Uhm, I don't think that is a welding table, but more so a surface plate. The thickness and ribbing are to add ridigidty to prevent the CI from creeping over the years.
A true heat sink welding table is different. I kid you not, at work we have solid copper table fixtures with integrated water cooling jackets and argon back gassing. I can't imagine the cost, not only of materials but R&D time. They look nothing like that.