Day 4 done (this morning) due to major around the shop chore work yesterday. All I can say is man did this open my eyes, going from the top of the swing to A6 I saw how much I am casting the club (muscle memory). Good thing - the shop door faces east so it casts my shadow nicely (almost as good as a mirror). Here's day 4 mistakes and all...
It's a bad habit that I picked up when I changed my takeaway. I used to cock my wrists, which caused me to fan the clubface open. I continually struggled to get it back to square, which of course led to high, weak shots that leaked right. It's an unconscious thing I do to check that I'm not fanning it open.
I belong to 2 courses here in Colorado. I walk one of them every time I play (unless I'm playing a scramble tournament) and the other is not walkable. The walkable course is open now, with specific rules. Many ride that course, one person per cart, 6' distance, etc. The other course is not open yet but we have a private cart for that one. It won't affect my play at all.
Index finger is a good trigger for it, too. I tended to feel it more towards the pinky side of my left hand when I was doing it which resulted in supination of the wrist in addition to flexion, thus hooding the club.