Configure a license-free standby replica (preview) for Azure SQL Database You can save on licensing costs by designating your secondary disaster recovery (DR) database for standby when using Azure SQL Database.
Configure a standby replica
You can designate a replica for standby when you configure a new active geo-replication relationship by using the Azure portal, PowerShell, or the Azure CLI.
To create a new active geo-replication relationship and designate your secondary database for standby in the Azure portal, follow these steps:
Step 1: Go to your SQL database [Here db1] resource in the Azure portal.
Step 2: Choose Replicas under Data management from the resource menu, and then select + Create replica to open the Create SQL Database - Geo Replica page.

Step 3: On the Create SQL Database - Geo Replica page, select Standby replica for Replica type under Replica configuration. Check the box to confirm you'll use the replica for standby.

Step 4: Provide a new or existing server for the new standby database and then use Review + create to do a final validation of your database and server details.
Step 5: Use Create to confirm your settings and create your new standby database replica.
Reference:
https://learn.microsoft.com/en-us/azure/azure-sql/database/standby-replica-how-to-configure