If you require to purge a buffer anywhere in a flow, use the Buffer Purge destination step.
This step allows you to purge any buffer in any flow without creating a new flow or extra steps just to purge the buffer after the flow does what is required.
NB: Please note that you are still able to purge a buffer before inserting, updating, upserting or deleting records. This step is to merely purge a buffer anywhere in a flow with only one step.
Illustrated below is how the step looks. Highlighted is a drop down list where you can select the buffer that you want to purge and then click on the Save button to save the step with the change.