Hey Phil, how very exciting to put your Flow super on for the first time! It does take a while for the bees to fully wax the cells up and I don’t see any there yet, but it’s just one snap from the very outer frame face. There could well be more progress toward the center. By the bees’ head-in posture I’d be willing to bet that waxing those cells is exactly what they’re doing! Did you rub any wax on the frames beforehand? If not, see if you can give them a quick pass with a chunk of burr comb you might snag during inspection of the brood area. It makes a huge difference in getting more bees up there and working.
Just keep an eye on the local flow conditions and check frequently to be sure the bees don’t begin to propolize those frames instead. That will be obvious dark reddish brown deposits along the cell seams, indicating they regard the F super as too much space.
Keep us posted on progress!