In other Serverless projects we use a single resource definition to include AWS CloudFormation scripts in our build/deploy. Where the resource file contained component definitions like DDBTable: in the root.
resources: Resources: ${file(resources.yml)}
However a new project contains a lot of AWS configurations so I decided to split it up. You can do that using the next syntax. However make sure your files start with the Resources: data type.
resources: - ${file(resources/resources-vpc.yml)} - ${file(resources/resources-db.yml)}
You can even mix and match inline and external resources
resources: - Resource: ApiGatewayRestApi: Type: AWS::ApiGateway::RestApi - ${file(resources/resources-vpc.yml)} - ${file(resources/resources-db.yml)}