How do I force restart my iPhone 6s Plus?

Hi there,

thanks for contacting Apple Support communities.

to Force Restart your iPhone 6s Plus, please:

1. Place your fingers on both the Touch ID Button and the Power Button at the same time for 10 Seconds until your phone powers off.
2. Once you see the Apple Logo, please release both fingers and allow iPhone to turn on.

if my instructions have helped you, please let me know below.

Thank you, and have a great day!

Killian.