I can't seem to get ballet flats to stay on my feet (wide forefoot, narrow heel and medium volume, thin ankles). I am looking into custom flats because I need something closed toe/closed heel but am very tired of wearing shoes in summer.

These are my options
a) two high ankle straps b) single strap around the ankle but slightly lower c) diagonal strap across the top of the foot.

Which of these styles has a reasonable chance of staying on? Returns are not an option in one case.

Other ideas?