I decided to put both 2 channels and their power supply circuits into one board. This will shorten all signal length.
The wiring is point-to-point. I forgot to take the picture underneath but it is quite tidy due to very simple design. The feedback resistors were directly soldered onto the chip's pins for the shortest distance possible.
The assembly took me the whole night but it was straightforward. I plugged in the power and after looking cautiously for smoke I plugged in the speakers and it made a nice sound. There was a problem though.
The Gainclone would make beautiful sound but after 30-40 seconds it would get into some kind of oscillation problem. The sound was like bbrbbbbrbb ... after some thoughts and investigation I pointed out grounding as the culprit. It was using one transformer with two 0-30 outputs. I changed the wiring as shown here and the problem was fixed.