You have to be the judge of what that means. But my own view (and I have built the NE Dory) is that you just want to sand it fairly lightly. Knock off pointy things and very sharp edges, but that's about it. If you have already filled the seams between the strakes, there will be some lumpy bits of fiberglass to deal with. And again you have to be the judge of how smooth you want it.

The big danger in sanding is that you may sand through the outer layers of veneer before fiberglassing, or that you may sand through the fiberglass afterwards. Don't make those mistakes if you can help it.

But everything can be fixed in a wooden boat. Stay calm about it all and don't try to build a museum showpiece. But, of course, you know all that from your prior building experience. The lapstrake construction of the dory makes it very strong, but also makes it hard to create show pieces.

Just one small expansion on Birch2's excellent advice - at your current stage of construction what you need to make sure of is that there's nothing to snag the fiberglass cloth when you lay it on the bottom. If you can run your bare hand over the bottom and not get any splinters, you're done sanding for now (but there'll be much more in your future).

Laszlo

   Excellent and helpful replies, makes sense.  Thank you!