Set riser boards to the marks and fasten them to the walls or side boards.
How to form concrete steps with side walls.
Tap the sides of the forms and risers with a hammer and jab a 2x4 up and down in the mix to drive air bubbles out.
Mix the concrete and bring it to the site in wheelbarrow loads.
You can do it like a wall build a wall set your risers and false form the inside of it.
The inner side wall form would be your tricky cut but could be braced one to the other.
To make the wall as strong as possible pour the concrete in layers no higher than 20 inches working from 1 end of the wall to the other.
A cap on the wall would be needed and you would want a thin mix on the wall but a thicker mix on the steps that you would pour first.
Use screws and a power drill to attach each riser form board to your stringers.
Before pouring concrete steps coat the forms with a release agent.
You would cut a form for the inside that would be similar to a stair stringer but set upside down.
Then pour your concrete inside the form using a chute or hose attached to the mixer.
To form a concrete wall first set up plywood boards on either side of your concrete footer and attach them together with wire.
If your not sure what that means its simply using a discardable material inside the box to make the sidewalls the desired thickness.
You can do this by laying each stringer form so the even bottom side of each stringer is flat on the ground and the zigzag side of the stringer is oriented with its points facing up.
A monolithic pour would give you the best outcome.
Assemble your concrete form.
Building formwork when forming between walls or other flat surfaces such as plywood where you will be able to mark riser locations positioning risers is easy.
The form for the exterior of the wall would be far simpler.