When building background knowledge, we want to include:
Vocabulary words that are important
Various perspectives on ideas, theories, events
We can find examples of these on the internet to include such as relevant articles, journals, books, websites, movie clips, videos from youtube, songs, etc.
I have created a simple building background knowledge freebie for you so that you can organize your curated information in an appealing manner and share it with your students via google slides.
I like using the internet but you can also create physical stations with books, realia and other physical artifacts for students to explore. Making a connection with the material helps comprehension and motivation.
No matter what subject and what grade you teach, you can find a great picture book to read. This also builds background knowledge and opens the class to a discussion. A discussion will also activate schema and identify gaps or clarify any misunderstandings.