On my 6+, the sequence is: press home button, tap Settings, Wi-Fi, Off. That's 3-4 depending on whether you count the home button.

On a 6s or newer, with 3D touch, you can cut it down to 2-3: unlock, force touch on Settings and toggle WiFi from the menu that appears. (That might be 1-2, I forget whether you can force touch and drag to what you want to activate, or whether it has to be a separate tap.)

I didn't know about using force touch on the settings app. However when I tap on the wifi menu entry that appears, I still need yet another tap to disable wifi.

Anyway, here's my count: 1. use touch-id to unlock the phone 2. press home to get to first screen with the settings app (if you aren't already) 3. tap Wifi 4. turn it off

You then need to navigate back to where you were previously.