I used a still more inefficient way of solving this room.
I grew the gel until it filled the north (horizontal) part of the "
L"
-shaped chamber. But I made sure to leave some gel babies in the northwest corner, in such a way that when I went over there I would be able to start cutting gel.
Once the gel filled the north part of the chamber, I manouevred so that a large number of gel babies spawned and filled the east part of the chamber, and so that the gel grew around those babies to form a cuttable shape. (This took a few tries to get right.)
With the "
L"
-shaped chamber full of gel and gel babies, the gel babies were standing on the pressure plate. I killed the goblin, made my way to the northwest corner of the room and first cleared the gel out, then took care of the remaining goblins.