small pole barn advice

when I worked as a surveyor, the City of Seattle tried to make their slabs less than 150 Sq ft, usually 12x12. They used smooth tie-bars between slabs to keep slabs from rocking independently from adjacent slabs, yet still allowing for expansion and contraction. They didn't use screen to hold the individual slabs together, but then they were pouring them a foot thick. LOL.
If it were me, I'd use the 4'x8' 6"x6" welded wire mats for reinforcement, and like what was suggested don't move the dirt and use it as fill, use new crushed rock, and well-compacted for all of your sub grade.