If you are a flat-footed, you have different issues in weight distribution for your feet. Try using 9to6 in all three thicknesses--4, 6, and 8mm--in sequence over a long period of time. It creates a nice healthy arch, making your feet more comfortable.
Save 24%. (estimated retail price: $57)
3x 9to6 Arch Support (0.15/0.23/0.31inch, 4/6/8mm)