
Since this dish contains quite a bit of cheese I normally don't grease or butter my oven dish but instead I sometimes coat the bottom and edges with a bit of tomato sauce. The pasta won't stick anyway more than it would with butter or tomato juice so feel free to leave it as it is if you fancy. Just like I did this time. ? Instead of plain tomato sauce you could also use any ready-made pasta tomato sauce like Bolognese or anyone you normally like or just have handy.
https://www.ramonascuisine.com/pasta-shells-filled-with-spinach-and-ricotta-cheese/