The basis of "no-recipe" cooking is knowing how to make a sauce. Think about it - a meal is often a piece of protein with some veggies and/or starch and a sauce over top, so if you know how to make a sauce, dinner is a snap!

Guidelines:

Roux: 1 part fat (oil, butter, etc.) 1 part flour, 16 parts liquid (broth, milk, etc.) e.g., 1 Tbsp pan drippings, 1 Tbsp flour, 1 Cup broth to make a roast gravy, or 1 Tbsp butter, 1 Tbsp flour, 1 cup Milk to make a Bechamel sauce (then add 1/2 - 1 cup of grated/shredded cheese to make a Mornay sauce.)

Cornstarch slurry: mix 1 Tbsp of cornstarch with 1 cup of seasoned liquid, pour over sauteed meat/veg in a frying pan/wok, then bring up to a boil until it thickens.

Reduction: in a wide shallow pan (e.g., frying pan) reduce the cooking liquid/juices until thick. You can also add wine, vermouth, Balsamic vinegar, cream, evaporated milk, or broth/stock to the pan and then reduce. Reduction time will depend on the amount of liquid and how thick you want the sauce.