5.1. The shower base flange is slightly slopped by design. At the locations where you will screw the shower base to the studs, it is recommended that you use
wood shims to fill the gap between the base flange and the studs.
5.2-5.3. Drill guide holes, and fix the shower base by screwing it to the studs. It is recommended that you screw 1 screw per stud, and aim for the center of the