(the brand name by Mark Spenard is the Foot Flexor)
First the traditional 3:
Then if you applied the idea and went from flexion to extension
you might try something like this:
To continue the progressive pattern of movement from flexion/extension
to lateral side bending requires what builder Mark Spenard calls the Foot Flexor
II, which he custom built for me. With this stretch version of a foot corrector
you can now develop flexibility laterally and challenge alignment through the
ankle when coming up onto the ball of the foot in plantar flexion.
I use them both, switching from side to side,
to really wake up the feet!