Have the GC mark out the walls.
Be there when they pour!
I'd make it a point to go and meet the concrete foreman and tell them what your going to do and where.
Strap on the horizontal right before the 90, strap again across both directions right after the 90. Whatever you leave I'd strap in the air up to four feet.
A real cool trick is to have ridge 90's, ridge vertical with a coupling and a coin right flush with
elevation. IE the finish of the floor. Granted it easier doing this againest the edge of the pad.
You can put the coin in and just tape it again.
In any case I'd 90, straping and leave pvc or ridge out of concrete and with 6-8" sticking out strap again, coupling and coin. You can bring it out from the wall to hit future panel or future run up or in wall...