Currently, it has dirt right against the house, the dirt level is flush with the lawn. There is already a strip of concrete with pebble stone finish dividing them, but I would like the bed to be raised. I plan on laying the flagstone retaining wall bricks on the concrete strip since it's providing a nice level solid foundation already.

I am thinking just having 2 bricks high which I think at 6" it will be a 1 ft wall.

Front wall is solved what about the back? The house has crawlspace and there is a vent in the area. Plus I don't really want the dirt to be raised and filled against the house anyway. So I need to build a back wall and provide maybe a ft clearance against the house. The dirt it has to hold back isn't a lot of volume.

Any suggestion what to use for this? Should I use redwood posts and fence boards to build the back wall?
Wood is easy and cheap but I would like something that would not attract termites, the moist condition with wood so close to the house concerns me.

Is there resin deck boards alternatives?
I'm open to all suggestions though.

Also, the kind of retaining wall bricks that I'll be using, the kind with the lip, Is it easy to make a 90 degree turn with them, are they just meant to build straight and convex walls? Otherwise I wouldn't know how the lips will interfere.