Could I build a curb to create a 3/12 roof pitch on a flat roof so a power fan can then be installed?

Air Vent's power fans are designed for residential applications (houses) on roofs with a minimum 3/12 roof pitch.

Air Vent's power fans are designed for residential applications (houses) on roofs with a minimum 3/12 roof pitch. It would be best to avoid building a curb and instead  install the power fan on a suitable pitched roof.