1. Launch the Shortcuts app.
2. On the Automation tab, select Create an automation for myself.
3. Select the condition - Application.
4. Check the Open option and specify the application in which we will enable the blocking.
5. Select an action - Start timer for 1 second.
6. Be sure to turn off the Ask before launch switch.
7. Save the automation, and in the Clock app, set the Timer action when finished to Stop.
Now, when the specified program is launched, an automation will be triggered that sets a timer for one second. When the timer expires, the iPhone screen will lock. So a stranger will not be able to use the application and, when trying to launch it, will receive a blocked gadget.
The owner of the smartphone will simply pass authorization using Face ID or Touch ID and continue to use the gadget.