This level will introduce the first mandatory use of the "Whistler", acquired two levels ago. It conists of a large, dangling metal pipe with an abundance of goo on it along with some sleeping spit-goo on a hill below.
Hold your cursor on the left side of the metal pipe and hold down M1 (Mouse 1). This will release bird-tweeting noises from your cursor which attracts all the black goo's to the estimate location around your cursor.
Use this to lure all the goo's to the other side, tipping the balance of the metal rod and making it tip down on the drool-goo's, waking them up and climbing onto the pipe.
Grabbing hold of them once they've woken up may be necessary in some cases.
Lure back all the goo's onto the right side using the Whistle (M1) again and tip the scale back over the pipe.
Build with the slime-goo's and the gravity pull from the pipe should start, finishing the level.