Is tha a pic taken from the exterior?I think I would do a black metal strip almost like a baseboard to close that off .

this is an inerior view btw

If it were me, I would cut two pieces of wood to match the post at 45 degree angles (where they meet in in the corner), just like what you’d see on an interior wall. You could do it with a hand saw and a miter box, but if you don’t want to, I’d call the doofus that screened your porch in and tell him to fix it.

I mean tomorrow I would squirt a big load of caulk in there as a short term solution. Long term you need a base shoe of sorts, up against concrete you probably want a synthetic material like azec which could be spray painted black and held in place with clear caulk.

I agree about the doofass but probaly a matching wood piece could work but I think I would still do black metal the same height as the bottom of the metal frame.

Backer rod and caulk, followed up by a Azek or PVC Baseboard as Hallett said above.

I would text whoever did this the picture and say if it is not fixed by next week the picture is going up on local social media as an example of his or her work.

In the meantime I'd be stuffing whatever I could into that gap to block snakes and mice from getting in.

Will there be any additional flooring?

Steel wool is pretty good at plugging mouse-sized holes. It would probably serve the purpose here, until a permanent fix is completed (whatever that happens to be).

Good point - it depends on what your time frame might be, and how protected the area is.