Explanation
Flow Builder allows you to create an automated business process that can update records based on certain criteria. You can use a scheduled flow to run once a week and count the number of open cases related to an account.
References: https://help.salesforce.com/s/articleView?id=sf.flow_builder_overview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.flow_concepts_scheduled_start.htm&type=5