I don't have any advice except that astilbe really likes a moist spot. I have some ferns that someone gave me that spread and are pretty tough in the shade. Astilbe only does well under my barn drips. I think hostas are less demanding than astilbe. There used to be a garden near Eureka Springs Ark. that had hostas on a shady slope.

It sounds very pretty!
My only slope is in a sunny area but I do have rocks and shade and have tried lots of different plants in my shade gardens. My trees have very greedy roots so plants that are drought tolerant do best for me.

I planted several creeping phlox on a slope (in the sun) and just put a couple bricks in front of each plant to hold it in place until its roots were deep enough to hold it there. That kept the rain from washing them away. I don't remember if I removed the bricks later or if they're still under the creeping phlox.
I think it will make a difference which way your slope faces. If it faces the north, it will stay more moist. If it faces the south or west, it will get some dappled sun and more wind in the summer.

I'm linking a photo I came across on the internet below. I like the way the rocks curve down(up) the hill, almost an s.

Here is a link that might be useful: {{gwi:1114067}}

Thank you, everyone, for the good advice. Christie, that Garden Coach photo is fabulous. I wish I had that kind of design talent!

I've been working on the two shady slopes and have just about finished them. I don't want to look at another rock or fern or creeper for awhile. lol. Couldn't lift the black lava rocks I have, so bought and carried in my back seat 219 lbs. of rocks in two trips from the Rock Yard on Shifferdecker. It's a neat place. They have a "pick yard" where they sell by the piece and there are some lovely rocks there -- a lot were too large for me to handle, but a man would have no problem.

Anyway, I'm bushed and I'm so happy the project is pretty much over. Only got one tick on me and he was just crawling. I took a "before" photo and will snap an "after" and post them soon.
Sunny

Here are my before and after photos. Since my young grandchildren love to play in what they call the "Green Room" (a shady place surrounded by a canopy of dogwoods) I will feel better now that it isn't so wild and wooly. Have a few iris to move (too shady for them now) make a path through the iris bed, and then I'm done.
Sunny

It looks very nice. I see you like frogs too. I have lots of frogs and toads.

Helen, I'm absolutely nutty about frogs. Have a few toad friends who live here and there, as well. Glad you liked it.
Sunny

You've put a lot of hard work into that area and it shows up beautifully.

Thank you, Jaceysgranny. It was well worth the effort.
Sunny