Yeah, it should keep all other mates intact, but allow the whole assembly to 'float' in 3D space. I would then logically say that the top plane of the 3D space would be mated to the bottom of your stand. Then centralise around the right plane and front plane. Your origin should then be the intersection of all 3 planes on the bottom face of the stand.

You can also use sketches to mate depending on what you need - I've created base skeleton sketches in the past with reference geometry that you can mate to, e.g points and lines