手掌
the palm and fingers when they are held straight and level
He hit me with the flat of his hand. 他打了我一巴掌。
She rubbed her cheek with the flat of her hand.
In her fury, she struck the table with the flat of her hand.
Don't hold the carrot with your fingers when you're feeding the horses; place the carrot on the flat of your hand.
With the flat of your hand, pat the dough completely level.
Sophia laid the flat of her cool hand against his hot face.
See also: flat noun (LEVEL GROUND)