The best way to learn something is to write about it, in public, but only if you care about learning. When you write, you are forced to organize thoughts into words. When you teach someone else, you feel obligated to understand the topic.

If you were secretly recorded during your next "deep work" session and had to watch it after, you'd probably find that 90% of the work you're doing is unnecessary, and most of the needle-moving tasks could be done in 2-3 hours, maximum.