What OAuth grant flow can I use with Chatbot (Chat Conversations API)?
Any OAuth grant flow works with Chatbot as long as you set the scope to 'read', 'write', and 'chat'. The choice of OAuth grant flow largely depends on your workflow. However, the most straightforward grant flow is the Implicit grant flow.
For more information on Chat Conversations API or Chatbot, see Getting started with the Chat Conversations API.