slipper - boots made of synthetic polymeric foam sheeting material comprise an upwardly flared foot - receiving throat having an upper opening with a first perimetral length to provide excess material for stress distribution and a lower opening having a second , smaller perimetral length to grip the wearer &# 39 ; s ankle . gussetted bottom soles also may be provided for additional width . an apparatus and method for making such slipper - boots comprise means or steps for simultaneously forming the heel of a leading slipper and the toe of a following slipper across an intermittently moving folded band of material , whereby slipper size may be varied by altering the time of movement of the folded band of material between formations of the slipper - boot heels and toes . material folding means are also disclosed .