Rainbow sandals is the brand...they conform to your foot with a memory type insole. Something to check out if you are into wearing sandals. They have a great warranty...along the lines of a free replacement if anything goes wrong with them if you have have not worn through the sole yet. Maybe I could see this slipping issue if I was to wear a generic foam flip flop say those from Old Navy come to mind, but with the ones I wear there is no issue at all.

I have even driven with my five fingers as well...those are as close as you can get to barefoot. Five fingers is a brand name not literally my fingers. Another shoe that if you do not know about is worth a look. You can get a great workout in them when hiking...etc.