Thaw strawberries in strainer over bowl to reserve juice
Once strawberries are thawed, measure out juice. You will need 1½ cups juice. If you don’t have enough juice, add water to juice to make a combined mixture equaling 1½ cups liquid.
In a medium saucepan, whisk together Jell-O and strawberry liquid until combined.
Place the saucepan over medium heat and cook the strawberry mixture until it comes to a boil, about 2 minutes.
Once it's boiling, whisk in the corn starch and water mixture. Bring back to a boil.
Once it's boiling, stir in strawberries and bring it back up to a boil. Then take off heat.
Serve right away or let sit if you want it cooler.