Spawning falling rocks like the Avalanche map ?

Can anyone point me in the direction to focus my learning on. I can make a mod of a rock with the jbeams. And I can see from studying the Avalanche scenario that LUE triggers are used to act as teleports. What I am not clear on is what to create to spawn the rocks in the first place in a scenario. I am thinking it has to be done with the flow editor but not sure.

Not asking for a full on explanation. Just point me in the direction and I will read up on it if I know what to read

Thanks !

 

I hope you get answers. It might be in the wiki ? seems like a nuanced problem though. There is a new wiki but don't know how thorough it is

 

Thanks, I will look again, its may be something that is too complicated to explain.