Place half of angel food cake pieces in the bottom of a deep 8-x-8-inch or 9x9-inch baking dish in an even layer. Spread 1 cup cherry pie filling over top of cake. Top with remaining cake pieces in an even layer.
Whisk together vanilla pudding mix, whole milk, and sour cream in a large bowl until slightly thickened and smooth, about 1 minute.
Pour pudding mix over top of cake and spread evenly.
Spread thawed whipped topping over pudding layer. Dot with remaining 1 cup cherry pie filling. Using a toothpick or spoon, swoop and swirl pie filling into the whipped topping. Refrigerate, uncovered, for at least 8 hours or up to 12 hours. Garnish with sliced almonds.