Theoretically, that's all that should be requiredl, but in practical terms, as far as I'm concerned, I go ahead and do a little tap dance across the width of the flints edge while I'm doing it at all...for me personally it isn't worth the time it takes to search for and find that precise tiny flat spot and then try and knapp it out...I just do the whole edge when I knapp one.

Another good trick I've learned, is that when I stop shooting to clean the lock off with an alcohol rag (about every 10 shots) I loosen the jaws and flip the flint over...from bevel up to down (or vise versa) and adjust/tighten it back in place.

This alternating practice almost seems to let the flints "self-knapp" themselves...wear more evenly, don't seem to develop flsat spots, etc....and it's particularlygood if you're usiung a reasonably flat flint, so when you flip it over it still has the slightest downward shaving angle at frizen impact time, and isn'tlining up too straight/square into the face of the frizzen.

PS:
By the way...my whole conversation here is based upon using Black English Flints...if you're using those "sawed" agate flints that look like a grade schoiol pencil erasure, this knapping discussion does not apply to them...they do need to be resharped with a diamond file or diamond grinding wheel, Mizzy wheel, etc