The most effortless way to ensure that all new Amazon Elastic Block Store (EBS) volumes are encrypted at rest is to enable EBS encryption by default in all AWS Regions. This setting automatically encrypts all new EBS volumes and snapshots created in the account, thereby ensuring compliance with encryption policies without the need for manual intervention or additional monitoring.

AWS Documentation on Amazon EBS encryption provides guidance on enabling EBS encryption by default. This approach aligns with AWS best practices for data protection and compliance, ensuring that all new EBS volumes adhere to encryption requirements with minimal operational effort.