The easiest thing to do when you aren’t sure is to refer to the diagram at the front of the manual as to how the layers work.
The flex and static sample slots are shared among all patterns, parts and banks in an entire project. This means that if you use slots 1-10 and then change them in another bank or part, they are changed everywhere.
However each part can use any of the samples in the pool. so part 1 could use 1-8 and part 2 could use 9-16. bank 2, part 1 can use 17-24, etc.
To recap:
A pattern contains all of the steps, the time signature (if project is per track), and an assigned part.
Each part allows you to assign a sample for each of the tracks, the track parameters (lfos/effect/etc) and 16 scenes.
each bank contains 16 patterns and their parts.
each project contains the assigned sample slots and (16? 8? banks, i forget how many) and the bpm (annoying that it’s a per project). Also all of the project settings (recording settings, project settings, midi, output, etc.)
a set contains multiple projects (no limit i think?) and an audio pool, which is really just a file system of samples that you can use for the sample slots.
I’m sure i’ve missed some details as this was all off the top of my head, but hopefully this makes more sense. I would strongly urge you to keep rereading the manual every month or two. Things make more sense, you pick up tricks that you didn’t notice before, and the octatrack’s possibilities will start opening up to you. It’s also good to refer back to it whenever you want to do a thing you haven’t yet done, or haven’t done for a while. It’s also worth watching all the official tip videos, and checking out others from around the place.