If using Instant ClearJel, stir sugar and precooked cornstarch powder together in a small bowl until thoroughly mixed before stirring into the strawberries. Otherwise, it will lump.
The amount of sweetener will depend on the sweetness of the strawberries.
If you use frozen strawberries, it's even faster since you don't have to rinse and hull the strawberries. Plan ahead and let them thaw in the refrigerator overnight.
The nutritional analysis is for regular cornstarch since the database does not have instant modified cornstarch.
Variations:
Use a food processor instead of mashing.
Substitute raspberries. Increase the sugar as needed.