This is simple to repeat
Select a constructor. Give it a move order that will take 2 turns to complete but not travel the full distance. For instance, if the constructor can move 10 tiles in a turn, order it to move 15 tiles. The goal is to have movement points left over in the next turn.
Next turn, click the end turn button (it should say that it will move all ships with move orders). This will cause the game to try to move onto the AIs turn, but is forced to wait until the constructor is finished moving. Instead of finish moving, order it to construct a starbase. In this moment the starbase screen will be open. However since the last ship no longer has unused movement points left, the game determines that it must be the AIs turn and will try to move one while you are in the starbase screen picking starbase modules for your starbase.
Edit: I didn't expect the text to turn red. I did a //me. If this conflicts with the mod voice (often red), I'll change it when asked.