The Cube and Mini should be kept on a smooth, flat surface, where there is proper ventilation. When wifi sharing, you want your Mini or Cube to be close to a window to maximize range. Avoid placing your Cube or Mini on the floor where they will gather dust.
When using a Mini or a Cube with an Edge Extender, it is okay to keep your device in a server room or back office and run an ethernet cord to the Edge Extenders.