No cornstarch? Thicken a sauce or gravy with flour or arrowroot. For 1 tablespoon cornstarch, use 2 tablespoons flour or 1 tablespoon arrowroot.
1 tbsp cornstarch = 2 tbsp flour (or 1 tbsp arrowroot)
Whisk the flour into a little cold water first, then stir it into the sauce and let it simmer: flour needs cooking. It thickens gradually and looks more opaque. Stop when the sauce coats the spoon.
Use flour: 2 tablespoons for every tablespoon of cornstarch the recipe calls for. Whisk it into a little cold water, stir it into the sauce and simmer for a few minutes until it coats a spoon.
All-purpose flour (2 tablespoons per tablespoon of cornstarch) or arrowroot (1 to 1). Flour is the better pick for gravy and stew. Simmering the sauce uncovered to reduce it also thickens it with no starch at all.
Use flour. Cook the flour in a little butter for a minute, whisk in the milk, then simmer and stir until it thickens. Arrowroot can turn slimy with dairy, so flour is safer for milk sauces.