How do you get Siri to answer your question without holding the home button?

See if the following articles answers your question:

• Use Siri on all your Apple devices - Apple Support
• Devices that support "Hey Siri" - Apple Support

Once Siri “beeps” you can let go of the button. Or go to Settings/Siri & Search turn on Hey Siri, and just say “Hey Siri” followed by your question, such as “Hey Siri, how old is Queen Elizabeth the second?” or “Hey Siri, what’s today’s weather?” or my favorite when I’m out and about, “Hey Siri, get me home"