Different ways you could do it, but the one from Melev's Reef you need to plan out where everything will go. Not sure if he did a video or talked about it on his Youtube channel, but it's probably something as simple as a piece of MDF with some spacer on the back to keep it away from the wall slightly which is where the cords run behind it, basically "dry fit" where everything is going to go, then drill appropriate holes to put cables through.
Although looking at the reflection off the surface it may be made out of acrylic, the guy is an acrylic fabricator after all. But same principle for placement. For things like the ecotech drivers may be as simple as some velcro to hold them on. Yeah on further review I'm almost 100% certain he made that out of black acrylic, I see little shelves for the power bricks in the bottom corner. But MDF is more easily available and cheaper to work with, but the principle is the same. Holes for cords to go through, some standoff/spacer on the back to allow cords to go through, if you want to be classy you can use cord grommets so you don't have to see through the box.