This custom resource is based on cfn-lambda, you can see this project for more advanced configuration.
Clone the repository on laptop. Inside the root folder:
$ npm install
$ npm run cfn-lambda-deploy
This command deploy the lambda helper on your default AWS region and us-east-1, us-west-2, eu-west-1, ap-northeast-1. To change this configuration you can follow this link
You can test the custom resource by running example/user-pool.cform. This only parameter is the name of the lambda function created during the installation.
All parameters usable is the same of the parameters use by aws-sdk to create a user-pool