If you are looking for classic sandals for very low-volume feet, you might take a look at Easy Street. I've found them at Macys but I think other stores/online outlets carry them too.

The M width works for me but they also carry N, W , and WW.

My feet are normal length and width but almost totally flat across the instep. Most sandals I try, even some with adjustable straps across the instep, are too loose across the instep to be secure on my feet, so I tend to go back to the same brands when I find ones that work.

I just received the brown ones below and they are PERFECT. The strap that crosses the foot at an angle is a tiny bit loose but it does not matter because the other straps are tight enough. Just a bit of a heel and quite comfortable. I like the fabric wedge-covering.

Most of their sandals seem to be man-made, which I can't wear for closed shoes because my feet perspire so much, but for sandals it's ok. The footbed feels like suede, so in theory good for hot humid days, They are pretty inexpensive to begin with, and on huge discounts right now - around $30.

I'm thinking of ordering the black espadrilles and/or the gold/black ones. All their sandals come in multiple colors.

p.s. the finds all seem to say "Daisy Street", which looks like a typo on the Macy's site. Search on "Easy Street " to find them.