Hi!!
Sorry for the long time to answer...
I make them using the measurement of the foot they will fit, so they are very comfortable and good for walking on the nature because they grip the foot very well.
I think I spend about 6 hours to make them (without counting the time that takes the glue to dry).
This model comes from Mexico but they are long time ago very popular in Canary Islands too. They are called "huarachos".
Cheers!