basement stairs riser question

As part of the basement fixup, I am replacing the stairs. Currently, 2x stock nailed to three stringers. The walls are on both sides of the staircase. I am going to replace the 2x treads with oak treads. To maintain the current riser height, I am putting down 3/4 plywood. . Before I install the oak treads, do I put the riser on first butting to the plywood, then the oak tread -or- does the tread go down first, then the riser goes on top of the tread? . Thank you for your time.