Is it possible to perform Includes with flask?

By default, Flask uses Jinja2 as its template engine. See Jinja's Template Designer Documentation how it's done.

From: http://jinja.pocoo.org/docs/templates/#include

template.html

{% include 'banner.html' %}
{% include 'sidenavigation.html' %}
{% include 'content.html' %}
{% include 'footer.html' %}