Ok, trying to picture this.
If I'm standing with my back flat to the wall of the house, there's no slope to my front, or from side to side?
I'm sort of guessing you mean it's flat over to the fence, then pitches down at (or under) the fence, yes?
If it's like this:
__________ |
\_|_ {fence}
Then, angle-of-repose is your enemy. Established grass sod will hold a 40º from the horizontal. "Chunky" DG will hold 40-45º; finer DG only runs 30-35º; as you exceed those values, rain will wash away anything you put in there.
Metal edging will work, for a short while. If you are really lucky, it will not "rotate" down into the drop off from erosion. Much.
If you use concrete edging, you'll have similar issues unless you "terrace" it up--and you'll need three horizontal courses for 2 feet.
Which kind of gets you to the inter-locking landscape blocks--they are 8" high, so you need three horizontal courses for 24"
Those landscape blocks will have some sticker shock, especially when compared to metal edging (which is not cheap). But, you can do the block in batches (and your back will likely prefer that, too).
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Standing guard, even sitting behind a desk
Occupational hazard of my occupation just not being around