With a large population, you can afford to specialize your workforce. Create dedicated districts for farming, resource gathering, and production. Use the 'Profession' tab in the 'Information' window to fine-tune worker assignments. Ensure you always have a buffer of unassigned laborers to handle construction and resource clearing tasks.
Monitor your population's age distribution. A large elderly population can strain your healthcare and food resources, while a lack of young adults can lead to labor shortages. Build more houses to encourage population growth if needed, but always ensure you have the resources to support new citizens. Consider building a Graveyard for deceased citizens to improve happiness.