More in Windows Walls and Doors
Saw through the sole plate just inside the doorway studs and remove the offcut, so that the doorway is clear. Be careful not to saw into the finished floor. The frame is now ready to be covered.
Mark a notch (area to be cut away) on the wall plate so that it will sit over the baseboard and lie flush on the wall. With the wall-facing side upward, saw along the guide line to the depth marked by the pencil lines on the edges. Use a bevel-edged chisel and a hammer to remove chunks of wood, working down to the depth required. Position the plate against the wall and secure as normal.
Use a masonry drill bit to drill through the sole plate and into the concrete floor (image 1). This will guide your fasteners into place. Use hammer-in fasteners through the drilled holes to fasten the sole plate securely into place (image 2).