This tutorial will make either of the last two examples public to the world! Note: this tutorial does not cover adding security to your device.
Create an ngrok account https://dashboard.ngrok.com/signup
In the terminal of the Raspberry Pi....
Install and set up ngrok: https://dashboard.ngrok.com/get-started/setup/raspberrypi using the APT method
Once you've completed the curl installation, Run the config command to add an authtoken to the raspberry pi's configuration file. As shown >>>>>>>>
Copy the Static Domain command and paste it into your Raspberry Pi Terminal.
Deploy your app using a static IP.
Run your Flask app and go to the URL to see and interact with the app. Get to your URL quickly from your Ngrok account by clicking on Cloud Edge and Endpoints.