I'm still working on My slab prep. I've got all the sod up and I use a power rake to take down the surface 1 inch at a time, It looks like Ive been in the back with a roto mill for asphalt. I'm almost done I think 1 more time should do. With this clay, when it gets wet you cant hardly get around on your hands and knees on a 1% grade!!
Ive thought about foldable fill also Its cheaper than concrete. 40 years operating equipment,, I too am too old for this shit.