For the sake or argument though, if you do have ten seconds you want to chop up into a billion little slices and edit the fuck out. (keep in mind some of these steps might be different based on how you have reaper configured)
You just slice up the waveform, disable the grid lines (red circle) or disable snapping and drag them about to exactly the miliseconds you want.
Then you highlight every item in the section and right click and go "glue items" and it will reassemble them into a single item.
Depends on how you have it configured. Reaper is highly customizable, one of its main strengths. Not everyone uses it the exact same way. Stuff like the visibility of the lock icons and count in and etc. etc. etc. and pan law is all user configurable.
Once again though. I don't see a benefit to doing it that way. Unless you are doing like, djent mixtests. If you absolutely must have silence on a guitar part, I would automate the volume envelope instead of slicing it up. That's just cheesy.
That being said though, everyone has different workflows. No two people are the same. I'm not sure exactly what you meant. I personally wouldn't slice up a ten second clip into a billion different pieces and drag them around, but that doesn't mean you can't get good results with it. I think it's easier to just do more takes.
If it's something you can't re record on the fly. Yeah, that skill is more important. If it's a guitar part, retracking it is way easier.
I personally don't like punching in section by section, since that's not as "trve" as playing it from the top. But if I wanted to change the guitar part at the third chorus and I had to play the earlier three minutes of the song just to get there, shit would be untenabley time consuming.