Frequently Bought Together

Name: Frequently Bought Together
Namespace and key: custom.frequently_bought_together
Type: Product - List of products

In product setting:

Result:

Choosing the metafield (version 1.3.0)

The Bought together products section reads this content through its Frequently bought together metafield setting. The default key is custom.frequently_bought_together.

Keep the default key above and it works with no extra setup.
Or rename it: create the metafield under your own namespace.key (for example, your brand name), then set Frequently bought together metafield to match.
Reuse on one page: create one metafield per copy (for example custom.frequently_bought_together and custom.frequently_bought_together_2) and point each Frequently bought together metafield at its own key to show different content.

See How to setup Metafield in version 1.3.0? for details.