This is the simplest and fastest install of flask with virtualenv for developing.

1. Upgrade and update ubuntu (recommended)

sudo apt-get upgrade
sudo apt-get update

2. Download the shell file and run it

wget https://github.com/piNot3/nitrousIO/raw/master/flaskapp.sh
bash flaskapp.sh

3. Restart Nginx to apply changes and run the flask app

sudo service nginx restart
sudo start flaskapp

4. Preview the result

Preview > Port 3000

When you make modifications, you can restart the flask app

sudo restart flaskapp

Tips

Right click on folder flaskapp > Set "flaskapp" As Root

Click on 3 vertical dots > Show Hidden Files