Using newExternalWorkflowStub correctly?

We tried using newExternalWorkflowStub within a current running workflow (as opposed to continueAsNew) to kick off another workflow so we can pass in a new workId. We saw an error stating

Caused by: java.lang.IllegalStateException: Cannot start a workflow with an external workflow stub created through Workflow.newExternalWorkflowStub

We were wondering if we used newExternalWorkflowStub correctly? Or is there another way to start a new workflow within a workflow with passed in workId?

Use Workflow.newExternalWorkflowStub for connecting to an already running workflow.
Use Workflow.newChildWorkflowStub to create a stub that can be used to start a new child workflow.

Here is the relevant section of the documentation.