When something is described as being as flat as a pancake, it means it is very flat.
It's a perfect day for sailing because the sea is as flat as a pancake.
Cycling around here is easy, the countryside is as flat as a pancake.
If you fall flat on your face it means you have failed at doing something, or embarrassed yourself by making a mistake.
If we don't get any funding, this building project will fall flat on its face.
I fell flat on my face at my performance. When I started to sing I forgot the words. It was so embarrassing!
A pancake is a thin, flat, round cake prepared from a batter and cooked on a hot griddle or frying pan. Traditionally they are tossed, or flipped over, in the frying pan so that both sides are cooked. In Britain, they are associated with Shrove Tuesday, commonly known as Pancake Day, when perishable ingredients had to be used up before the fasting period of Lent began.