I use the following approach  Beef stew meat (I think it's beef chuck) Soak in cold water for 20-120 min Pressure cook for 12 min Refrigerate Next day, hope to lift the solid fat out  Sometimes the fat freezes into a nice solid sheet - which is great! Other times it's tons of little pieces which is a bit of work to separate How can I best ensure the solid sheet? 
I assume the fat has just been emulsified in the stew's liquid, so it will not form a large mass. I'd slowly reheat the stew and cool it down again so that the fat can properly rise up to the surface. 