MissAdventure
I've spent a lot of hours checking out comfy sandals, as my feet swell, a little, a lot, on the top, underneath even, at times, and it varies every day.
I still havent got any, becausr its much more helpful to hear "straight from the horses mouth", as it were.
I know the feeling! In the recent hot weather, I was wearing my wide-fit Croc sliders/slip-ons (whatever). As you probably know Crocs have holes in the uppers. My feet swelled up THROUGH the holes [hmmm] and I could hardly even get them off! I got a pair of cork-soled (cool) open sandals from Pavers in Wide Fit. The sort where you can adjust either of the two fake buckles with velcro. Winner!

