Simmer uncovered to reduce liquid
Mix cornstarch with cold water, then stir into sauce
Mix flour with butter to make a roux, then whisk into sauce
Add a beurre manié by kneading equal parts butter and flour, then stirring in
Stir in tomato paste for tomato-based sauces
Add mashed potatoes or potato flakes
Blend in pureed vegetables
Add cream, cheese, or yogurt for dairy-based sauces
Use arrowroot mixed with cold water
Use tapioca starch mixed with cold water
Add ground nuts or nut butter
Stir in bread crumbs
Add a slurry of rice flour and water
Let sauce rest briefly after cooking to thicken naturally