Preheat oven to 375 degrees F. Oil a 9″x13″ pan and set aside.
For the topping, mix together rice flour, first measure of corn starch, turbinado sugar, almond flour, almonds or oats (if using), baking powder, and zest. Stir in melted margarine or coconut oil. Put into refrigerator while assembling the rest of the crumble.
In the oiled pan mix together the fruit. In a small bowl, mix together sugar, second measure of corn starch and salt. Toss the fruit with the sugar mixture until evenly coated. Pat out fruit until an even layer. Take crumble out of fridge. Break topping apart with your fingers and sprinkle the topping on top of the fruit evenly.
Place baking pan onto a jelly roll pan to catch any boil over that may happen, then place into the oven. Bake for about 1 hour and 25 minutes or until fruit is bubbly to the center and the topping is set.