Grease a 13x9x2-inch (3-quart rectangular) baking dish. Set aside.
In a medium saucepan, stir together granulated sugar and cornstarch. Stir in water. Cook and stir until thickened and bubbly; cook and stir for 1 minute more. Stir in cherry pie filling and almond extract. Set aside.
In a large bowl, mix flour, oats, brown sugar, and salt. Cut in butter until mixture resembles coarse crumbs. Press 2 cups of mixture onto bottom of prepared baking dish. Spoon rhubarb evenly over crust. Spread with cherry mixture. Combine remaining crumbs and the nuts; sprinkle on top.
Bake in a 350 degree F oven for 40 minutes. Serve warm or at room temperature with ice cream or whipped cream, if you like. Makes 12 servings.
