If the area is complex or multiple pours are needed, break the project into smaller pieces and calculate the concrete needed for each individually. For instance, when measuring a slab that is not a simple rectangle, try breaking it into different sections and measure the yards needed for each...
If you plan to paint the interior or doors of the cabinets a different color, then you should measure and record those figures separately, but the measuring process is the same. Measure sides and doors, then multiply. Do the same with small areas and then add to come up with the total...