OBM Deck Template with Offset Grade Line

How does one set up a deck slab template when the profile is not located at the alignment? In my case the cross-sectional shape of the deck is shaped like a simple gable roof but the grade line is not located at the peak (where the alignment is) but rather 23' to the right side. If I create the template with the WP at the alignment, then the deck will be placed too low because of the crown drop. Please tell me how to do this or point me to a video describing this issue.