This page provide links to some tools and examples for the three options.
To adopt an OER as is, you can simply add the link to the syllabus and emphasize it's FREE or low-cost to buy a print.
Step-by-step guides for selecting and adopting an Open Textbook:
To modify an Open Textbook:
To publish your creative work as OER or adapt/remix OER into a new work, check if the OER to adapt or remix have any built-in authoring tools available from the repository. For example: