Todays stupid question is: How do you get to the back of your rack?

There is no "stupid question" flair so "Help" it is...

We're redoing our basement and we're making a 20ft desk using countertops and kitchen cabinets. (It's a multipurpose gaming/activity room) And I had the brilliant idea to build a rack into one of the cabinets. Either by buying a pre-made 12U-ish rack frame, or do something custom with some studs and "racksides" (whatever you call the part with the square holes that you attach your gear to). Not full depth ofcourse, I only have a kitchen cabinet to work with (about 55cm). But with these types of hard mounted racks, how do you get to the back? Or do you just make sure everything is connected before you attach it?

I have considered putting a pre-made 12U frame on drawer slides and make the whole thing slide out. But heavy duty, full extension slides are expensive!

Any suggestions or examples?