Q:

Where is the root folder of a Meteor app?

I am trying to set up SSL for my meteor app and need to verify control of my domain for the SSL certificate provider. They want me to place a sslfile.txt file in the root folder of my domain.
I wanted to confirm that the root folder is the app/ folder. Is this correct? 
The file should open when I go to www.myapp.com/sslfile.txt
Reference (Method 3):
https://support.comodo.com/index.php?/Knowledgebase/Article/View/791/16/alternative-methods-of-domain-control-validation-dcv

A:

I think that's /public folder
documentation here

