Hardscaping around shallow tree roots
We have heavy clay soil and a well-established tree near a fenceline with many exposed roots, and I'm sure many shallow ones that we don't see as well.
We want to build some brick raised beds along this fence and around the tree. We know not to build a raised bed directly around or against the tree, and instead wanted to build a 4-6 foot brick ring around the trunk and fill it with large river rocks to allow it to breathe and still tie in to our raised beds along the fence.
For most hardscapes, you generally dig 8-12" down, lay a course of gravel, sand, and then your brick.
Given all the roots, this wouldn't really be possible without seriously risking hurting the tree. Are there alternatives to making structurally sound hardscape footings/foundations which can go on top of shallow roots?
We haven't finalized a design, and we will keep in mind that shallow and exposed roots need to maintain their access to oxygen and water. What are some of our options to keep the tree happy and also have aesthetically pleasing hardscape planters?
In short: how can I make structurally sound hardscape around shallow and/or exposed roots without damaging the tree? Or is this generally not possible?