Preheat Oven to 400 degrees Fahrenheit
Combine the sugar, salt, gluten-free flour, gluten-free oats in the bowl of a food processor.
Cut the butter into 8 large pieces and place in the food processor bowl.
Pulse the food processor about 20 times to cut the butter into the dry ingredients. It should look crumbly. Pulse more, if needed.
Add the chopped nuts to the crumble mixture and pulse a few more times.
Pour the mixture into a bowl and let chill for at least 15 minutes during which time you make the filling.
Put berries, sugar, salt, nutmeg, cinnamon, lemon juice, and orange liquor or zest into a bowl, and gently mix with a spoon until the berries are well coated. Set aside and have a cup of tea while you wait for the crumble topping to finish chilling.
Evenly spread the filling into a baking dish, tart, or pie pan.
Spread the crumbly topping evenly over the blackberry filling.
Pop the pan into the center of the preheated 400F oven and bake for 35 minutes.
You’ll want to let the crumble sit a bit before serving, but if you just can’t wait, place a scoop of ice cream on top to help it cool down. That will do nicely!
For Individual Servings: Divide the filling into ramekins, top with filling, place on a baking sheet, and bake as above.