There are 3 parts to a WorkSpaces Bundle; image, Hardware, and Storage. When working with Bring Your Own License (BYOL) in WorkSpaces Core, you create your image outside of AWS (Due to Microsoft Licensing) and import into Amazon. You can read more on that process here - https://docs.aws.amazon.com/vm-import/latest/userguide/vmimport-image-import.html
Once in AWS, you'll convert to AMI and import the AMI into WorkSpaces Core. - https://docs.aws.amazon.com/workspaces-core/latest/pg/infrastucture-setup.html#import-image
After you create a custom image, you can build a custom bundle that combines the custom image and the underlying compute and storage configuration that you select. You would then launch/create the WorkSpace and customize it, creating you gold image. This is also a point at which you can use UEM to customize your gold image. - https://docs.aws.amazon.com/workspaces-core/latest/pg/infrastucture-setup.html#deploy-desktop
After you create a custom image, you can build a custom bundle that combines the custom image and the underlying compute and storage configuration that you select. You can then specify this custom bundle when you create a new Horizon 8 Automated pool - https://techzone.omnissa.com/resource/deploying-omnissa-horizon-amazon-ec2-and-amazon-workspaces#create-images
Thanks,
Dan