I managed to rivet one of the flaps together today. I started out by clecoing the whole thing together and then removed the spar. I then used the rivet gun and bucking bar and riveted the row of rivets that joins the top and bottom skins. After that I riveted all the inner ribs to the skins in the same manner.
I then took the inboard end rib off and riveted the platenut and the FL-706B to the rib.
I clecoed the rib back on and clecoed the spar on as well. I blind riveted the ribs to the spar and then used a squeezer to rivet the bottom skin and the hinge to the spar.
Then I moved on to the top skin which I had to rivet with a rivet gun and bucking bar because I couldn't quite reach the line of rivets with a squeezer.
Finally, I riveted FL-706B to the FL-706A and riveted the end ribs to the skins. I used a MK319BS rivet on one of the trailing end rivets because I could not get to it with a squeezer and it was the same rivet that was used on the other side for the four rivets that are not accessible.