Roll out into a 12 inch round and place into a 9 or 10 inch deep pie plate. Tuck the excess pastry under the edges and flute the edges with your fingers or a fork.
Add the dissolved corn starch and stir gently continuing to cook for one minute or so. The fruit mixture should be thick and jammy. If not, use a little more dissolved corn starch. The amount of cornstarch may very depending upon the juice content of the fruits being used. A little more or less as needed is advised.