How flat is "flat"?

It is commonly said that Kansas is "flatter than a pancake." But it turns out that if you scale a pancake up to the size of the Earth, even Colorado is flatter than a pancake. All those big mountains? They're nothing to a pancake scaled up to the size of the Earth.

So, when we say that the Earth if flat, how flat do we mean? I can see small mountains out of my window. Sometimes they have snow on them when there's none here. A few hours' drive from me, there are really big mountains. And if you go to Tibet or the Andes, you can see really, really big mountains. Obviously, no flat-Earther would deny the existence of mountains, hills, canyons, etc.

If you know that mountains exist, as do flat earthers, why do you ask? None of us claim mountains do not exist.

It is commonly said that Kansas is "flatter than a pancake." But it turns out that if you scale a pancake up to the size of the Earth, even Colorado is flatter than a pancake. All those big mountains? They're nothing to a pancake scaled up to the size of the Earth.

So, when we say that the Earth if flat, how flat do we mean? I can see small mountains out of my window. Sometimes they have snow on them when there's none here. A few hours' drive from me, there are really big mountains. And if you go to Tibet or the Andes, you can see really, really big mountains. Obviously, no flat-Earther would deny the existence of mountains, hills, canyons, etc.

If the earth was flat :
By "flat" ,  I am assuming that "flat" is in reference to a straight line, drawn at sea level, from "ice wall" to "ice wall" , in a  cross-section of a flat earth.
Mountains and land , etc.   would  be drawn at elevations above or below sea level above this line.
There are some places on the earth where the land is below sea level
Oceans would be drawn at depths below sea level below this line.
I assume this would be taken into account if the earth was flat.

I got the knowledge. From reading your post.