I had 2 litters born 12/24 and 12/29. Of the 17 babies born - 10 survived through weaning, etc.
One of them - the biggest buck - is already over 8 pounds (almost 8 1/2 pounds the last time I checked). He's 16 weeks old I guess?
The smallest - a doe is a bit over 5 pounds.
Most of the rest of them are in the 6-7 pound range I'm guessing (I've already rehomed four of them).
I have another litter that was born 3/11 to Nyx (who is my largest flemish). They're about 6 weeks old and I'll try to weigh them tomorrow. One of them is definitely bigger (a buck that I like)...the others are sort of smaller. She originally had 13 in her litter but it is down to 7.
I'm sure other flemish giant breeders will pop in here.
I would not mind selling an 8-10 week old to a good home as long as it had made it through weaning ok. However - I would be selling the "pet" quality - meaning - it probably won't make the weight I want it to make as an adult. Perhaps it will top out at 12-14 pounds instead of 15 and above...
I can tell that by the bone structure and if they have narrow legs and feet.