How to call CMDB IRE when creating CI using Flow?

We have built catalog items and it has variables like Name, serial number, OS, RAM etc. Once the user submits it the catalog item, the FLOW will get executed and creates/updates the CMDB.

We dont want to give direct/write access to CMDB tables and we have DECIDED to go with this approach.

Now, to avoid the duplicates, we need to make use of the CMDB IRE in the FLOW. How to do it? 

Looking for steps to implement the same.

Thanks in advance!!!