How to set the realityView at the bottomTrailing edge of the volume?

I have no idea how to set the realityView at the bottom-trailing edge of the volume. Could someone help me?

var body: some View {
        RealityView { content in
            if let scene = try? await Entity(named: "Volume", in: realityKitContentBundle) {
                content.add(scene)
                bookEntity = scene.findEntity(named: "Book")
                crossEntity = scene.findEntity(named: "Cross")
            }
        }
        .toolbar {
            if (isShowToolbar) {
                ToolbarItemGroup(placement: .bottomOrnament) {
                    Text("The toolbar is shown")
                }
            }
        }
        .gesture(tapGesture())
    }

I have tried several ways, but none work, including adding a zstack to align with the bottum.

For now, the bounds of my volume are as follows: