For some reason the phrase “frog legs” helped me remember. Not sure why but it was something silly that I could think of easily. Also you can think of trying to get the back side of your knees to touch the saddle (For dressage at least). Where I ride your toes should be in, but I guess just a different instructor and style. Hope this helps!
@catrionakozijn yes, your knee should be on the saddle but very lightly without pinching and you should have the ability to turn your knee out and "open" it when you need. I need to practice this because of the horse I ride and my problem is that I never "open" my knee and also pinch with it.