My husband's sandal broke where you put your toes. This sandal wasn't all that old and the sole was still in a good shape, so I decided to repair it.
First thing I did was to make a hole where the strap goes in between the big toe and the toe next to it.
Then, I sewed on a narrow nylon webbing strap that I had at home and threaded through he hole I made. I tied the webbing strap on the back and made a knot. I also decided to use a glue gun to secure it on the sole.
It seems wearable again, so that's good. This is a pair of Keen sandals. If anyone associated with Keen sees this, please use a durable material for the sandal. It just rubbed and broke off. (I am guessing they are probably hoping that we buy another pair when this breaks, but my tendency is to avoid the brand that made products that broke in a few months of use...)