Sorry, If you dont know how to build in FRD mode, why bother posting on this issue -_-
I will tell you how to construct in FRD.
Select your command station.
Select engineer.
Hold SHIFT CTRL and V and left click.
THe game will build 5 (CTRL) Engineers. When they are constructed, they will FRD immediatly. Because they were ordered construction while holding V.
Do the same with Remains Rebuilder.
They will Idle once constructed, unlik Engineers.
I havent tried Tech's suggestion yet.