Squeeze excess moisture from spinach; place spinach in large bowl. Add ricotta, eggs and half the parmesan; mix well, season.
Spray the bowl of 4.5-litre (18-cup) slow cooker lightly with cooking oil. Combine sauce and pesto in medium bowl, season; spread ½ cup of the sauce mixture over base of cooker.
Place 2 lasagne sheets in cooker, breaking to fit. Spread one-third of the spinach mixture over pasta; top with one-third of the sauce, then 2 more lasagne sheets. Repeat layering, finishing with sauce.
Sprinkle with mozzarella and remaining parmesan. Cook, covered, on low, 4 hours or until pasta is tender.