For someone with a tiny bit of experience with BGA and SMD components, getting a hash board ready would take no longer than an hour.
That is a vast oversimplification of making hash boards...
This is a very high power density application that requires special attention to the thermal properties of the boards and where the chips mount. Specifically, the need for very thick power planes and a dense pattern of thermal vias under each of the chips to pull heat away from them and transfer it to the backside heat sinks.
May I refer you to forensics I did for AMT back in 2014 regarding why their hash boards were going up in flames
https://bitcointalk.org/index.php?topic=569769.msg7610684#msg7610684