Here is the relay board fully built but without any external connections to batteries, amps or PSUs.
Given the size of the vero board, the left and right channels are as far apart as possible and likewise for the pre and power amps. I am expecting crosstalk between channels to be very low indeed. Obviously left and right channels for the pre amps are not so far apart but they are of much lower signal levels so this should not be a problem. Look at the previous post ‘Relay Board Layout’ to see what components are what.
Since the components are not soldered to copper track pads on the reverse side, hot-melt glue has been used to hold them down. Otherwise all the components would fall out when the board is turned over to be soldered up.
See this Liquiphonics page to know why relays are needed: