Catch all in voiceflow

How do you trigger a ‘catch all’ intent in a specific flow but all blocks are choice blocks, not open listening for user intents?
So, if you have an app about the environment, and the user randomly types ‘pizza’ for example, how do you trigger a ‘get the user back on track’ message? Whereby the System says, I didn’t catch that, I can help you with A or B…
Thank you!!

Do you mean like using an Else path like this?