That's lovely! I'd enjoy that spot too.
Native plants (and other non-invasive, garden-worthy ornamentals) shouldn't need any amendment to the planting hole or fertilizers. Rocks in the soil won't bother plants a bit, and help hold the hill together, but bigger ones, and bigger tree roots can often prevent digging in particular spots. Moving over a few inches is often necessary. It's much easier to dig a smaller hole for a smaller plant, but that does require more patience to wait longer for the plants to get bigger.
Leaving the debris on the ground doesn't mean that you wouldn't pull whatever unwanted sprouts come up (and should keep the ground softer, making the sprouts easier to pull.) You've already made the connection between bare ground and dry ground. Leaves are wonderful, free mulch, nature's plan for the forest. That bag looks like the start of a nice compost pile.
Avoiding any kinds of rows is the #1 rule when going for a natural looking planting. What a wonderful spot to continue what nature has started!
