Okay update time. I finally got my shipment of lauralee's leftover 3M color quartz, and I was able to finish the substrate off. Now there is a much more secure slope coming down from the base of the wood and rocks. So now I've finally got the dang thing filled with water!
As I was filling I noticed that one of the beads of silicone that I applied to keep all the individual pieces of wood from floating had apparently not held. So one of my branches, a key piece, IMO, floated up and away.

I had to reposition it, which is much more difficult to do once you've begun filling the tank, and eventually had to just accept the fact that I wouldn't be able to keep it in its original location. I then found another "good enough" place for it, and shoved it deep into the substrate, underneath a rock. I won't say which piece got moved, try to figure it out for yourselves.
And here a few pics:
Right now I'm temporarily using a powerhead for oxygenation and circulation, but it will go as soon as I figure out what filter to put on this thing. Also, the water is very stained due to the tannins from the manzanita, but I'll eventually clean that up through some purigen.
I just wanted you (yes, you!) to see where I am with this tank. Happy Holidays, everyone!