A free resource can stand on its own. Choose a small task you can help someone finish, and make the instructions complete enough to use without another purchase.
Choose a complete task
Keep the scope small and useful. A one-page checklist can help someone prepare for a particular event; a short worksheet can help them make one decision. Avoid calling an incomplete excerpt a complete solution. Define what the reader should have done by the end, then include the material needed for that result.
Make the instructions clear
Explain where to begin, what to fill in, and what to do next. Add an example if the task might be unfamiliar. Test the file on another device and ask someone to follow the instructions. Free material still needs a clear filename, readable text, and working links.
Describe it honestly
Tell people exactly what is included and who it is for. If you mention another product, explain why it is relevant without making it necessary to complete the free task. When sharing, follow the rules of the place you are posting. A request for a free resource does not itself establish permission to send marketing messages.