The Flex theme includes a multipurpose and flexible Page section. The Page section allows you to create a separate internal content page in your Shopify Admin and then add it to another page.
Add a Page
To create content for this section, create a page in the Pages admin. While you’re creating a separate page, think of it more as a container for the content you’ll be creating.
Note that the section will only use the content (and HTML code) from within the page content but won’t include the page’s header, navigation, sidebars, or footer.
You can also use the column layout to create a page within a page — a large section with an effective layout that can provide users with information without having to load a separate page.
This section can also be used to add third-party widgets. If you need to include a third-party widget, such as a social media feed, video, map, certification badges, or seals, you can paste the provided code into the code view of the page content and then add it as a section to a page.
Connect the Page
Click Select page under Content page to assign the page.
In the Background settings, you can select the Background color, add a Gradient to the background and if you've added a gradient, choose the Gradient rotation.
The options under the Width setting include Half, Standard, and Wide. Selecting Wide will spread out the full width of the screen and Half will only span half of the width. Selecting Standard will keep the section in a container and not spread the full width.
You can choose to add space (padding) above and below the section by adjusting the Top spacing and Bottom spacing settings. Use the Left spacing and Right spacing sliders to adjust the horizontal spacing.
The Animation setting will determine how the feature appears as it loads. The options for animation are None, Fade in, Fade in down, Fade in left, Fade in right, Slide in left, Slide in right, and Zoom.
Add Custom CSS to the feature for further tweaking. You can even create your own CSS class here, as well. Check out this article for more information: Flex Guide: Custom CSS Feature