You cannot storyboard a stranger's answer. You can storyboard the machine that will catch it: interview coverage, b-roll modules, and the sequences you already know (a process, a walk, an archive insert).
Interview coverage as a tiny board
Two or three frames: wide of the room, MCU, CU. Note eyelines toward the off-camera brain. That is enough for an editor. Do not draw the subject's yet-unspoken emotion.
B-roll as a shot list first
A list of inserts and wides beats fake pictures of a factory you have not seen. Promote a line to a frame when the location is locked. Inserts · shot list.
Sequences you *can* board
Anything with blocking you control: a demonstration, a reconstruction, an opening title walk. Treat those like film.
FAQ
Is boarding a doc a waste?
Boarding the unknowable is a waste. Boarding coverage and modules is how you still have a day when the interview runs long.