I'm currently having fun in class with navionics! I'm searching my local lakes for flats. What do you guys consider a flat in regards to depth and size? 

To me it's relevant to the lake and surrounding areas. A flat could be a few hundred square feet to the entire back half of a mile long cove. 

Flat area any depth.

Can be 20 or 30 feet or much more or just 10 inches.

Think of your table top as a flat area, the 30" drop to the floor as a break and the floor area as another flat.

The table top being a small flat, the floor being a bigger flat, size is relative to area you are fishing.

Tom

Flat: with out any marked humps or indentations

Can be found at any depth from bank shallow out to deepest water in the body of water.