I've been wondering the last few days if I'm flatfooted after randomly reading that the test is whether your inner edge/arch touches the floor while standing.
This area of my foot does indeed touch the floor but if I slightly push my knees outward/open up hips it doesn't, which makes me wonder if it's just that I've got a slightly knock kneed posture sometimes.
I tend to push my knees out a bit nowadays but it was a conscious effort that has now become second nature. What started it was my knees aching a bit after the barbell squat, particularly when getting to around 100kg which is a fairly heavy squat for a woman. Suggestions online were to push my knees out which really helped. I then realised it felt like a more stable position.
However, I want to be sure I'm not sort of walking on the edges of my feet as that might not be good either. It's hard to tell as maybe that's how most people stand and I'm just not used to it. Aside from the arch all my foot touches the floor but it feels like more weight is distributed on the outer edge than the ball of foot/big toe.