I understand that the main purpose of the slice machine is to build reusable UIs, but I have a potential client where there marketing teams knows how to code. What is the best way that a marketer who knows code can "build whatever they want" in a slice. I was thinking of using a repeatable rich text field allowing everything but it seems kind of awkward to switch between writing code and then having an open div tag, then having another rich text field with an image, and then closing the div tag in the next code section. What is the easiest way to allow them to do whatever they want? Everything I'm coming up with just isn't all that intuitive.
I'm not sure I totally understand your use case completely, if the users can develop whatever they want then why use a CMS? Why not give them access to the code directly?
However, if you want to add the functionality you've described you can follow the guide here: