There should be a slight downward tilt towards the drain. But many systems are just laid flat on the basement floor/ceiling joists.

Thank you! Mine laid flat....it never fully drains like that

Many pans also have an irregular floor shape, with two drains. Water runs out the primary drain most of the time, but if it plugs up the water will start flowing out the secondary drain that is mounted a little higher in the pan. The secondary drain may also have a water sensor that can be set up to turn on an alarm buzzer, or to turn off the A/C if the water gets that high.

Bruce