I have purchased many pairs of Clark's slides.  I like them because there is no back on them to rub on my heel bumps, and also because they come in wide to fit over my high arches.  The sizing is usually very consistent and they have decent arch support and are always so comfortable - especially after I have worn them a few times. (the leather does stretch a bit over time)

This style was a bit tighter than most across the arch and loosening the buckle didn't help much so I chose another style instead.