I've sewn these simple slippers for my daughter's dance classes. For this project I bought scrap leather, although an old bag or jacket can be used. I also needed cotton fabric for the lining and an elastic band to thread around the ankle. I followed the instructions at Sew-ing.com (I don't read Japanese, but could figure out from the pictures).
And here is my pattern for size 27-28, printable on A4. For the linen approximately 1 cm must be added along the inner side of the upper part (the section without the dashed line). You will need the extra to fold and stitch the linen to the leather top.