Staking the footprint
The outline goes down first, and it is the cheapest moment in the whole job to change your mind. A staked line sitting on the actual ground is easy to shift a foot one way, square up a corner, or pull back from a tree you had not noticed from inside the house. Once stone is compacted and forms are up, moving the footprint means undoing real work instead of pulling a few stakes.
Stripping and grading
Sod comes off next, along with the soft dirt underneath it, since organic material rots down over time and takes the grade with it. The dirt is then cut to a fall that sends runoff out toward the yard instead of back toward the foundation.
This is where a site with real slope or heavy clay takes longer than a flat, well-drained lot. The subgrade, the natural ground once the sod and soft dirt are gone, decides where every drop of rain goes for as long as the slab is there, so it is worth getting right before anything else happens on top of it.
Stone base and compaction
Crushed stone comes in behind the grade cut, raked out over the footprint and compacted until you can walk it without the surface shifting. Over clay, how well that stone gets packed decides whether the finished slab stays where you put it or starts moving on you a few winters in.
Compaction is not a step you can eyeball and skip. Stone that looks flat but has not been packed will keep settling under load long after the concrete is down, and by then the only fix is tearing the slab back out.
Forms, then steel last
Once the base is right the formwork goes up, staked to take the shove of a loaded chute without giving. Those forms are the finished dimensions of the job, so they get walked and checked over before anybody calls for concrete.
Steel comes last on purpose. Wire mesh or rebar is tied off into a grid and then carried up on chairs, which puts the steel at the depth it was specified for. Left lying on the stone it is only weight in the bottom of the pour, with no concrete underneath it to grip.
Each step depends on the one before it
None of this is arbitrary ordering. You cannot compact a base properly until the grade under it is cut correctly. You cannot set forms to the right depth until the base they sit on is finished. You cannot lift steel to the right height until the forms establish where the top of the slab will actually be. Skip ahead on any one of them and the mistake gets buried under concrete instead of caught while it is still cheap to fix.