In article ,
Bertie the Bunyip wrote:

An old rule-of-thumb I remember has it that aligning the flap with a
down aileron gives you the best (most lift) flap position (assuming, i
presume, that the ailerons deflect to maximum effectiveness=lift)

Never heard it but it sounds like a good bush piloty sort of thing to do.

My flight instructor, a former drug-smuggler, taught me that very
technique.