A blank of flexible sheet material used to form and article of footwear upper and an article of footwear having a sole attached to the upper. According to one embodiment the blank of flexible sheet material includes a main bottom portion having a front toe area, a rear heel area and opposed sides, said main bottom portion being in the general shape of a foot sole. A front strap portion having an elongated shape extends outward from one of the opposed sides of the main bottom portion near the front toe area and having a free end, and a pair of heel-strap flaps extend outward from opposite sides of the main bottom portion near the rear heel area and configured to form an enclosed heel portion and a rear strap of the shoe upper. According to another embodiment the front strap is formed separately from the main bottom portion and pair of heel-strap flaps.