I bet Mary at www.marywalesloomis.com would know how to do this. 

I wrote her an email because I also would like to know how to do this.  My daughter goes through flip-flops like water.  They are always breaking.  And the price of them now is really getting up there.  I could have her make her own because now that school is done for summer, she has not a thing to do.   

Why don't they bring back jelly bean shoes?  Those were cheap and lasted a little longer.