Last night I did finally succeed in figuring out the things I didn't comprehend, so I was able to get the pouch started. The big victory was getting the increases to work and be symmetrical. (It was very important to me to keep it symmetrical instead of just accepting an asymmetrical project.)
Now that I'm on the second half, I just did my first row with decreases and I'm proceeding vert slowly and deliberately in effort to make sure I keep the symmetry going.
I have a pretty good knitting instruction booklet that specifies that k2tog slants right, and that while s1, k1, psso slants left, it is that SSK that is the mirror image of k2tog. So, on my first run through my first decrease row, I had done s1, k1, psso, I went and undid that and replaced it with a SSK.
One of the things that has happened to me since I started knitting is that I have acquired the ability to read what is going on in the yarn, and identify correct stitches and incorrect ones, and really see and understand the mechanics of how it's going together. When I was very novice (as opposed to what I am now, which I would call "advanced beginner"

) I could not even "see" the rows. I did not know how to count how many rows had been knitted. If I didn't count from the start, I wouldn't be able to figure it out along the way.
Now that I'm half-done with this sling, I fear that I don't have enough of
this cord left on the spool to finish it.

So this may end up being a practice piece anyway.
One last question (for now, at least):
Is there a specific reason for the design to have an odd number of total rows?
Would anything change if it were an even number?