"foot slipping" is correct and can be used in written English.
For example, "I nearly fell when my foot slipped on the wet pavement."
I could feel his foot slipping away.
I use the metaphor of a foot slipping off the curb and jolting, that I often used to have in dreams.
Grubman gets into the car, puts it in reverse, and then twists around to see if anyone is behind her, her foot slipping off the pedal as she does so.
Driving hard to his right, Camby planted on his right foot, slipping into a split, and had to be helped off the floor after spraining the medial capsule in his right knee.
The former beat the comatose rearguard with the same familiar ball around the back and the latter was unlucky to see his shot rebound from Hart's left post, the Austrian's standing foot slipping as he unloaded with the right.
The subject of "Tammy" is the very definition of the middle class — its nonexistence, with one foot slipping into poverty, dependency, and despair and the other perilously clung to by those who've climbed to higher economic echelons and reach out a helping hand (and then, with safety momentarily restored, offer a lecture in self-sufficiency).
If my foot slips, I'm gone.
His foot slipped; the machine automatically kicked on.
Wong turned to get back, but his back foot slipped, and he was caught.
But try on a shoe, and your foot slips into a whole new identity".
"When I turned to get back," he said, "my back foot slipped out".
