1. Dig the area 100mm extra + desired slab thickness, 150mm?
2. Compact the sub-base.
3. Lay PE sheet/plastic sheet.
4. Lay 100mm of crusher run.
5. Compact the crusher run again.
6. Lay single layer of brc A6/A7 with spacer.
7. Pour concrete + floor hardener mix.
8. Broom finish for better tyre grip.
9. Grinder cut a line between existing flooring and fill with sikaflex.

The slab should last awhile.