The "3 hours on the counter" part got me because I used to be team soft butter all the way, like the softer the better so it creams up nice with the sugar. Then I did basically the same thing you did and got one giant cookie puddle and I finally got it. Butter that's too warm is already part melted before it even hits the oven, so the dough can't hold its shape and everything just runs. Now I press my finger in the stick and if it sinks in easy with almost no push back, it's too far gone, so I stick it in the fridge for 10 min to firm back up. Chilling the dough after mixing works too but thats a whole extra step I only do when I have the time.