I would agree that the things our children are the most creative at are those things where they were given the most unsupervised time to noodle around and do what they wanted to do. I consider unsupervised time one of the great advantages in life I was able to give them by being a SAHM.
We did avoid giving them amusements that were “pre-imagined.” We didn’t get them Lego sets with a picture on the box of what to do with the blocks. We gave them Legos and sometimes played with them ourselves and our kids picked up a few building techniques by watching us, but that was pretty rare. Our kids felt very free to combine building materials from different sets, so they got results that weren’t on any box. We didn’t buy a lot of art supplies, but they got all the scotch tape, duct tape, string and recycling (cans, bottles, cardboard, disposable tin baking pans, and so on) they wanted.
We didn’t hover around and insist they play Monopoly by the rules. It wasn’t that they didn’t play their games with any rules. It’s that they felt free to invent new games with different rules, sometimes. They combined games, they sometimes changed the goal of the game. They made their dinosaurs into action figures.
We did have rules, but rules that encouraged them to earn their flexibility: If you want to do your homework when you feel like it, fine, but you have to get it done without parental prompting. We did tell them how to do things, but we explained why that was the way we chose to do it and were clear about when we were obliged to do things a certain way and when we aren’t.