Edging around tree
I have a live Oak tree in my yard and would like to put some edging around it so the mulch doesn't leach out into the yard. The problem I am having is that the lawn is sloped. There is a 21 inch drop from the top of the mulch circle to the bottom. The baked enamel edging would probably work but I don't think it would look very good. Are there any type of paver stones that would work? Any other ideas? I've looked online and not really been able to find anything on this specific problem. I also looked around my neighborhood and it looks like most of the structures were built at the time of the planting. My main concern is that if I build something up so it is level all the way around, I'll have this big open pit on one side of my tree. My understanding is that I would harm the tree if I backfill around the tree with soil to bring it up level. The tree is 8 years old. My house has brick siding and I'd like the edging to look good against the background of the house. Other than that, I'm open to any ideas.
I would appreciate any suggestions.