There are certainly more complicated apple crisp recipes, but this one from a friend in Canada is quite delicious.
1/4 cup butter
1/2 cup flour
1 cup sugar
Butter a 9" square pan. Peel and thinly slice the apples and put them in the pan. Mix the butter, flour, and sugar and spread on top of the apples.
Bake at 350 for an hour.