I sell at a farmers' market and, no, flea markets are similar but the products do not mix very well with fresh fruits and vegetables.
Right now, the season is really winding down here. I've had a good year growing pumpkins and knew that they would carry us into October along with my wife's arrangements of dry flowers and such. (Frosts began well back in September.)
I've reached a point where I'd like to sell the pumpkins and call it a season. There are other farmers' markets here besides the one where we have attended for well over a decade. It wasn't just me who had a good pumpkin year. Push myself & product in where others have been attending every marketday all season? Might not even be possible. Applications may no longer be even accepted - market management has to keep their other vendors happy.
I have tried to use as much foresight as possible about production and have something to sell from the 1st to the last. That saves us a space at the market and builds a regular customer base. Just to jump in once or twice during the season isn't likely to work well at all. My advice -- find a wide place on a well-traveled road and do your best to make it an attractive place to stop. Don't give the stuff away unless it is to charity. And, don't forget: a compost pile is always hungry and you are feeding the soil organisms that make your ground fertile for next year.
We are each other's harvest; we are each other's business; we are each other's magnitude and bond. ~ Gwendolyn Brooks