I just focus on more bend in my knee to avoid the chair seat. But be careful when you do that because you may have tendencies to grip with your knees. It may help to look down at where your heel is, also. Align your heel then memorize what that looks like when you're looking down at it. Practice makes perfect!
You seem to have a nice, natural-looking seat.
Every great dream begins with a dreamer. Always remember, you have within you the strength, the patience, and the passion to reach for the stars to change the world. ~Harriet Tubman