Not slow burn—that has a lot of connotations. These are films that you have to relax into, that have a mood or tone they sustain, they can be slow burns or they can be entirely disinterested in burning. I've made this list so I don't have to keep warning people who dislike slow horror not to watch a film I rate well for the correct audience.
You already know if you're this audience. If you are, please enjoy;