Fly control in pig pen

First time raising two pigs for meat (red wattle). They have a 32'x32' pen (cattle panel and hot wire) that is woodchipped about 6" deep. Their housing is two cattlepannels with tarp, and lots of ventilation. They have chosen to deficate/urinate inside their "house" where its straw....I've been chipping the potty spot. This is keeping smell minimal, but so many flies! I've hung up a fly bag, but wondering what else I can do. Other sites say to use insecticide and that's not an option for me..... I'm thinking LAB? Diamaticious earth? More fly bags?

Hi Missy ;
Diamatitious  Earth works great.
My piggys  will poop in their "house" when they are weiners, but after they get big and brave (lazy and hungry)  they head for a fence corner or just the fence line.
I rake the poop into  consolidated piles and liberally sprinkle DE over it. I do this every few days if not sooner.
Flies quickly disappear.  So does the worse of the piggy smell.  I also feed  DE in  fairly large amounts with their grain.  This takes care of parasites and worms.
I buy a #50 sack of food grade DE at the feed store each season, and it is used up before the next.

I don’t know about the space available.  I rotate my pigs among 3 pens.   I am looking into putting in a 4th one.  So far, no fly problem.  I do lime up the ground right after I move the pigs out of a pen.

Is it possible to move their house to another spot? Then maybe they will use the old place to do their business?

We have only had one pig though it was so fun to watch it clean house every day.  It would move all the hay out then tidy up and then put all the hay back.  I thought all pigs did that. I guess I was wrong.

Get a Muscovy duck or two? They are great fly catchers but they also eat grass so you need grass around for them. In fact, I had a young female last year and was trying to decide what to name her - I decided "Venus" as in "Venus Fly Trap". The name stuck!  Muscovy are a meat duck and if you have one of each sex, they tend to reproduce like crazy, so do your research before considering this.  I do believe there are cattle farmers who used Muscovy as "organic fly control", but I've not read about pigs.