I'm still not sure you have anything to fix, especially if there's no pain or discomfort going on.
I'm a big boy but my squat looks similar to yours. You can see my feet shift during the movement but this has not caused any problems for me whatsoever in 2.5 years of squatting in hideous toe shoes.
One of the cues I use is "spread the floor" which tightens up my legs and glutes but also shifts some of the weight to the inside of my foot. Again, I've always considered this normal for my squat style.
As an aside, my feet are much stronger after 2.5 years of barefoot squatting. I have a much more pronounced arch and my wet footprint is much smaller than it used to be.
Here's what my feet look like taking 365 for a ride, done on Monday of this week. I think of driving through my heels during the movement, but plenty of weight shifts to the inside of my foot as well.