Order of work, patio, drainage, steps

[onionsa]

In the attached image I’ve tried to show the bits of additional work required as part of my patio project. Aside from the patio floor there is also an ACO drain running the length, a new gully just around the corner out of shot, a step to the back door and also a split level step up to the garden. I am wondering what is the best order to start the work in?
The ACO drain will be 1 flag away from the house.
The top step is at the same level as the grass.
The steps will be the same flag as the patio, layer on concrete blocks.

Many thanks

 

[^woody^]

Start at the bottom and work your way up

 

[onionsa]

Start at the bottom and work your way up

That is kind of where my mind had gone to this morning after posting, thanks for confirming

 

[jasonzyx]

But measure from the desired finished ground level down to ascertain the required depth, ensuring you have allowed for the required layers and amount of cover, and the drain levels/falls.