post https://api.fulcrumapp.com/api/v2/workflows.json
One of the tricky parts of making a new workflow is that you need each step to have their own unique ID (in UUID format). The easiest way to do that is by generating a random UUID (look up uuid generator on your search engine of choice to quickly find a new ID) and then using these new IDs in your workflow steps. Make sure that the next_steps array in a workflow step references the valid ID of another step in your workflow.
NOTE if you receive a "Unique index violation" error when creating your workflows, you will need to make sure that the ids of your workflow steps are unique in your organization.