Here are a few landscapes in which your main job is to invent a top or a bottom. That, and making them beautiful, of course.
The beautiful part comes mostly from not correcting or overpainting. This is an opportunity to see if it really is better to leave the paint alone once it's been applied. An invented landscape can't be wrong , after all,, unless you insist it is by trying to improve it. If you leave it alone you send out the message that this is the way it's supposed to be.
Invented corn field
If the color in your invented top or bottom is saturated, try and put enough pigment in the puddle to make it satisfying on the first try. Stay out of the water bucket unless your plan requires that you wash your brush.