Coat inside of 4-quart Crockpot™ slow cooker with nonstick cooking spray. Cut waxed paper circle to fit bottom of slow cooker (trace insert bottom and cut slightly smaller to fit). Spray lightly with nonstick cooking spray.
To prepare batter, whisk baking mix, granulated sugar and 2 tablespoons poppy seeds in medium bowl; set aside. Blend sour cream, egg, milk, orange peel and vanilla in separate medium bowl. Whisk dry ingredients into sour cream mixture until thoroughly blended.
Spoon batter into slow cooker; smooth top. Line lid with paper towels. Cover; cook on HIGH 1½ hours or until cake is no longer shiny and toothpick inserted into center comes out clean.
To prepare glaze, whisk orange juice into powdered sugar in small bowl. Cut cake into wedges; place on wire rack with tray underneath to catch drips. Spread glaze over top and sides of each wedge. Sprinkle 2 teaspoons poppy seeds over wedges; let stand until glaze to set.