Making a concrete surface level is best accomplished if the subsurface is properly prepared beforehand. The ground should be dug to a depth of 3 to 5 inches with a trench dug on either side. If the ground is mostly clay, an additional 2 inches of depth is needed to hold gravel, which will aid in drainage. If the surface is prepared with a fluctuation in depth of no more than 1 inch, your concrete will be level.
Measure and mark the area where the concrete will be poured. Use stakes or spray paint to mark the area to be dug up.
Remove all vegetation and soft ground from the area to be covered in concrete. If removing grass, reuse it in areas of the lawn that have bald spots or where a thicker lawn is desired.
Dig out the area to the required depth. Concrete usually sits 1 to 2 inches above the grade, so the depth of the concrete should be 3 to 5 inches. If the soil is mostly clay, dig an additional 2 inches in depth to leave room for a gravel base.
Dig a trench around the area's perimeter about 6 inches wide and 4 inches deep. This will make the concrete surface much stronger.
Smooth the ground with the flat side of a rake and fill in any low spots with extra dirt. Check for level by placing a level directly on the ground.
Tamp down the surface with either a hand tamper or a machine tamper. Pack the soil until you can no longer see a footprint when you walk across the surface. If adding gravel, pour the gravel base and tamp it down to pack it tightly. Check for level again.
Lightly spray the ground with water before pouring in the concrete.