Pull your pants down to your knees; your knees are in front of you when squatting and your pelvis rotates, so the feces will land behind your heels. Maybe wearing very baggy pants there might be a problem, so don't do it if you're a teenager and the year is 1994?
Ah, these are sommon in parts of the middle east I've lived. I've always done a few minutes of slavic squatting a day just to make sure I'll never crap my pants if I find myself constrained to using one of these.