This is an example implementation of supporting sending Lightning Email Templates from a Flow using @InvocableMethod
.
Example__c won't necessarily exist or have matching fields. It is in here to inspire what you might do.
If you want to try this unmodified, you'll need to create a custom Object with an API name of Example. It will need to have fields with API names Email__c (Lookup(Contact)) and ExampleEmail__c (String or Email).