PatTheAttorneyHi! Unfortunately Oak Street Bootmakers doesn't size by width. George, the founder recommends the below:
"We have found the Elston Last (which is what the trench boot is built on) to be very accommodating. Everyone with an E has comfortably gone with our standard width (which is the only width we offer). EE and EEE usually go half size up."
Hope this helps!
PatTheAttorneyWidth really isn't an issue. I wear an E and ordered my normal size, and there isn't any tightness at all. However, I feel like they run a half size too big. If you're more of an EEE, I would suggest taking your normal size. Any tightness should go away in time as the leather conforms to your foot.