How to create non mandatory dropdown field in Salesforce flow ?

Making non mandatory dropdown field is very easy and you don’t need to know any coding, just follow below simple steps:
Download JQuery and save it as a static resource by name “JQuery”.
Copy below Visualforce page
Replace “flow:interview” name by your flow name
If you are expecting any URL parameter then simply add it as “apex:param” as shown in code
Add your field names which does not need to be mandatory in variable “nonMandatory”
In your Flow, add “– None –” as first choice in dropdown.

OR
follow the below link for example.
https://www.jitendrazaa.com/blog/salesforce/creating-none-required-dropdown-field-in-flow/