Preheat the oven to 350 degrees F (175 degrees C).

Sift flour, sugar, cocoa, baking soda, and salt into a 9x13-inch ungreased baking dish; form 3 wells in flour mixture. Pour oil into the first well, vinegar into the second, and vanilla into the third. Pour cold water over all and stir well with a fork.

Bake in the preheated oven until a toothpick inserted into the center of the cake comes out clean, 30 to 40 minutes. Frost with your favorite icing.