This recipe is my own version, modeled after my own apple pie. Usually, this is made using ingredient amounts that basically include a pinch and a dash, a squeeze and a scosh. Finally, I made myself slow down and kind of measure everything out so that I could post it here. These are, of course, approximate.
I've written this to make four individual crisps, the way we eat it, but if you want to make one big crisp, just add 10 minutes to the baking time.
I don't use nuts, but if you want to add some nuts such as pecans to the topping, just replace about a 1/4 cup of the oats with them. Also, I'm not a huge fan of very sweet desserts - this even pushes the limits for me. If you prefer sweeter desserts, increase the sugars in the filling to your taste.