Coat the cavities of a standard 12-cup muffin tin with cooking spray. Coat your hands as well. Divide the crispy rice mixture among the muffin pan cavities. Coat the back of an ice cream scoop or small tumbler with cooking spray and use it to create an indentation in the center. Allow the crusts to set for 5 minutes. Fill each indentation with a spoonful of prepared lemon curd and top each treat with a ready-made meringue cookie.