O.K Here we go.
Best lift/drag is the speed you operate at to get from A to B with the least fuel burnt.Nil time considerations here.This is the "best range speed". With a Boeing FMC,one would derive this speed by entering a "cost index" of zero. " long range cruise " is or has a fuel burn of 1% above best l/d.
Now min. fuel flow is what it states.The speed that will result in the min f/f per hour.This is the speed one would hold at.One can derive this speed in Boeing FMC by selecting "present hold" (don't execute).
I hope this info makes some sense.If not re-query.