How to add a loading sequence/scene/etc. when importing something at runtime to avoid it going unresponsive?

Hello. The title speaks for itself. my Unity goes unresponsive when I import an .obj. the Editor and the built version goes unresponsive but its actually just loading the .obj. What can I do to stop/prevent it from going unresponsive and just create some kind of UI that shows/says its just loading and the reason why its hanging/going unresponsive is because its just loading the .obj file.