Might Be a Silly Question

Does anyone know any exercises or stretches that would improve sitting criss-cross? I am very inflexible but would love to be better about sitting on the ground criss cross with my students. I can rock a HIIT routine but when it comes to sitting on the floor I am a mess. When I have to do the butterfly stretch my knees are up to my ears because I can't put them down. I always stretch after workouts but I am wondering if my lack of stretch when younger is the problem and it's too late for me.