Step a: Create Role using execution-role.yaml in CFN resources folder.
Step b: Search for Mongodb::Atlas::FlexCluster resource.
(Cloudformation > Public extensions > choose 'Third party' > Search with " Execution name prefix = MongoDB " )
Step c: Select and activate Enter the RoleArn that is created in step 1.
Your FlexCluster Resource is ready to use.
Step 2: Create template using flex-cluster.json
Note: Make sure you are providing appropriate values for:
1. OrgId
2. ProjectName
3. Clustername