Preheat oven to 350 degrees F (180 C). Adjust two oven racks, one at the top third, and the other one on the bottom third of the oven. Prepare a 9x9 baking dish and lightly grease with butter.
Add almond flour, sugar, brown rice flour, tapioca starch, and salt into a large bowl. Add the chopped butter. Crumble the butter into the dry ingredients with your hands.
Add the slivered almonds and candied ginger. Toss to mix well.
Spread the crumble into a thin layer on a large baking sheet lined with parchment paper. Freeze for 20 minutes. Transfer half of the crumble and freeze it in an airtight container, up to a month (*Footnote 1).
Bake the rest of the crumbles for 12 to 15 minutes (*Footnote 2), until golden brown. Set aside to cool.
Prepare the apple while the crumbs are in the freezer.
Halve the apples, remove the corn, and sliced the apples to 1/8-inch (3-mm) thick pieces.
Add apple, maple syrup, lemon juice and cornstarch to a large bowl. Toss to coat well. Transfer to the prepared dish.
Bake until the apple turns tender, 45 to 50 minutes.
Add the cream into a tall bowl. Mix with a hand blender on high speed until soft peaks form.
To serve, portion the baked apple into serving plate, top with the crumbles, with a scoop of whipped cream on the side (*Footnote 3).