Embedding a Machine Learning Model into a Web Application
I am not sure you would get any such tutorial regarding the same. It is more like asking how to build a software.

For example, consider you have to build an ML model for doing Sentiment Analysis before a post comes onto your feed, this is how you need to build the system:


The ML model would constitute the backend of the software, as it is just another algorithm we are using for building the software.
The plots or the feed you want to display to the end user would constitute the front end, which would include the templates and the views. 


The above can be achieved through an MVC framework. The data can be sent back and forth the server and the client through a protocol.

Useful link

In case, you want to integrate it with an external system, then create an API for the above system which you have built and let the other systems use your software/app by calling your api.

Now, create a simple SlackBot which can interact with your API with some certain commands, and display the relevant results in the group.

Example of such a system