We will follow the AWS CLI command option to create the corresponding CloudFormation template, in order to create the app client.

The Resources and Outputs sections should look as follows:

Resources:
  MyUserPoolClient:
    Type: AWS::Cognito::UserPoolClient
    Properties:
      ClientName: 'My Cognito User Pool Client'
      ExplicitAuthFlows:
      -USER_PASSWORD_AUTH
      RefreshTokenValidity: 30
      UserPoolId: !ImportValue MyFirstUserPoolId
Outputs:
  ClientId:
    Description: 'Cognito user pool Client'
    Value: !Ref MyUserPoolClient

We can also add a template format version and a description.

We can now create the CloudFormation stack with the user pool client, by executing the aws cloudformation create-stack command.