Hey. In BMW i8 we've used HTML+CSS to make it. So it is actually an HTML element that is using css
transform: translate to position in screen, and uses
transform: rotate(45deg); to be rotated 45 degrees.
That might be not most efficient way to do it, but it worked.
If you make them as 3D object, you can change how they interact with depth buffer. If you select material, and then untick depth test and depth write, then they will be always rendered on top of everything
I've used inspector in dev tools, and highlighted actual element for you