The goal in this project is to create a platform measuring 7 inches high and about 7 inches below the front door’s threshold (the threshold is about 14 inches off the ground and steps should be around 6 or 7 inches high).
The platform will be created from bluestone treads around the edges (measuring 2 inches), cobblestones (measuring 5 inches), and a 1/2" inch mortar joint. If the cobbles are set slightly below grade, this will give the 7-inch height for both the platform and threshold.
The sides (which don’t have the cobblestone risers) and the center (made of 1-inch multiple bluestone) should be demolished to create a surface that, when the material is added, is level. As you demo, check your measurements with a measuring tape.
If the area between your platform and house doesn’t have flashing, install some. Whether it's rubber or tin, flashing will save your house’s foundation by preventing rot.