2 1/2poundsmixed applessuch as Granny Smith, Macintosh, Honeycrisp, and Pink Lady, peeled, cored, and cut into 1/2-inch-thick wedges (about 6 medium apples)
1/4cuppure maple syrup or honey
2tablespoonsbourbonor rum or water
1 1/2teaspoonsground cinnamon
1tablespoonfreshly squeezed lemon juice
Vanilla ice creamfrozen yogurt, or Greek yogurt, for serving
Place a rack in the center of the oven and preheat the oven to 350°F. Lightly coat a 9x9-inch or similarly sized baking dish with non-stick spray.
In a medium bowl, stir together the oats, almond flour, brown sugar, pecans, and salt.
In a microwave-safe bowl in the microwave (or a saucepan on the stove), melt the butter. Pour over the top of the oat mixture. With a fork or rubber spatula, stir until the crumbs are evenly moistened.
To a large mixing bowl, add the apples, maple syrup, bourbon, cinnamon, lemon juice, and cornstarch. With a big spoon, stir to combine.
Scoop the apples and any liquid that has collected at the bottom of the bowl into the prepared baking dish into an even layer. It will be very full. Nudge the apple slices around a bit so that they lay fairly flat.
With your hands, squeeze chunks of the crumb mixture together to create clumps of assorted sizes, and place them on top of the apples. Scatter any remaining crumb mixture over the top.
Bake the crisp until the apples are tender (you may need to use a fork to peek down underneath that generous topping and check on the apples) and the crumb topping is crisp and deep golden brown, about 45 to 55 minutes. Check the crisp halfway through, then periodically during baking; if at any point, the topping browns more quickly than you would like, tent the pan with foil to protect the crust, then continue baking as directed. Serve warm with a big scoop of ice cream.
TO STORE: Refrigerate crisp in an airtight storage container for up to 4 days.
TO REHEAT: Rewarm leftovers in a baking dish in the oven at 350°F.
TO FREEZE: Let the crisp cool completely. Tightly cover it or place it in an airtight freezer-safe storage container. Freeze the crisp for up to 3 months. Let thaw overnight in the refrigerator before reheating.
TO FREEZE UNBAKED: Tightly cover your apple crisp, and lay it flat in the freezer for up to 3 months. Let thaw overnight in the refrigerator, then bake as directed.