More spinning beams! Firstly put a little eyeball on top of the tall column so that it will fall down to the red button. Lay a normal beam flat across the second ditch, put the giant eyeball on top (on the left). Set up a spinning beam alongside, so that when the entry ball hits one end, the other end launches the giant eyeball.
Yashar Kamyar also sent in this better solution:
Luisa has a reliable way to complete the level too: