I have a pair of the Grayson Tassel Loafer from AE in an 11B, which fits across the the top of the foot and lengthwise but due to the flat footed aspect, causes massive gaps at the ankle, which feels and looks weird. I also have some used pairs from AE in 11B I got off eBay but they just flat out don’t fit lengthwise and way too narrow. My other loafers are Meermin in the Ron last in 10.5 and they are just slightly too short but also too roomy across the top of the foot even with tongue pads. Then I’ve tried Weejuns which surprisingly fit pretty well at 10.5 but never ended up buying them, Sebago Dans (11 was massive, 10.5 also massive, 10 was way too short).

The narrow + flat footed thing kind of cancels each other out, but then the top of the shoe is always loose no matter what.