Whisk 2 cups cold whole milk and 1 (3.4-ounce) package instant vanilla pudding mix in a medium bowl until thickened and smooth, about 2 minutes. Let sit until fully set, about 5 minutes.
Arrange half of the angel food cake cubes (about 4 cups) in an even layer in an 8x8-inch square baking dish (at least 2 inches high); gently press on them to level.
Spoon half of 1 (21-ounce) can cherry pie filling (about 1 cup) evenly over the cake. Top with the remaining cake cubes.
Pour the pudding mixture over the cake cubes and spread into an even layer. Spread 1 (8-ounce) container thawed frozen whipped topping over the pudding in an even layer.
Dollop the remaining cherry pie filling over the whipped topping, then use the tip of a knife to gently swirl to create a marbled effect.
Cover and refrigerate until set, at least 4 hours or up to overnight. Just before serving, sprinkle with 2 tablespoons toasted sliced almonds if using. When serving, wipe the knife between cuts for the cleanest-looking slices.
