Where is the relative airflow coming from in a glide decent?
Huh? The relative wind comes from the same direction at a particular airspeed. Climb, descent, doesn't matter.
To a rough approximation, an aircraft at a particular airspeed will have, say, a 6 degree AOA in level flight, descents, and climbs. This is slightly affected by the fact that in climbs and descents, part of the vertical forces supporting the airplane are provided by thrust and drag respectively, requiring less lift from the airplane. But in shallow climbs, the effect is small.