The UiPath Picture-in-Picture feature is a good way to isolate the process, but it won't completely block user input. For that, you need the aptly named Block User Input Activity in UiPath Studio.

Block User Input Activity
The UiPath Block User Input Activity will stop the user's keyboard and mouse from being able to interact with the RPA process running in UiPath's Picture-in-Picture window.
There is an escape mechanism though. If the user does need to break into the PiP window, an escape key sequence can be set on the Block User Input activity. When this hotkey or escape sequence is entered, the block user input functionality is disabled and it's possible to once again send keyboard input or mouse clicks to the RPA robot.