I don't agree with the 10k hours bullshit popularized by Gladwell, google a bit about him and you will see he admitted that all his "non-fiction" books were actually insight porn more than teaching you anything useful. I liked his books too until I realized he just made up nice pop-culture stories and pretended to tell you the truth.

That said of course you have to have some level of practice and knowledge about whatever you want to create before you can be inspired to create something new. That doesn't mean you can be creative just because you've had practice. I remember Huberman and others talking about circadian rythms and how people are more creative at night, can't remember the exact reasons, might've been something about cortisol being lower then. I do believe cortisol levels are a hint as usually you are less creative on "uppers" like caffeine or adderall than you are without them because you always want to do things while on them and not actually think deeply about your problem.