If you can’t measure productivity, measuring time is not an acceptable substitute.
I manage several teams one of which entirely work from home. It’s no different to them being in the office.
I can message or if urgent I can call them whenever needed. We arrange times for catchups just to see how we’re all getting on and each week the agenda is set. They trust me, I trust them, everyone just gets on with what they need to do.
It would be very apparent if anyone regardless of where they work started to procrastinate. I don’t need to wander around with my arms crossed glaring over everyones shoulder seeing what they’re doing every minute of the day - I don’t have time for it either!