This pdf file is made in standard American terms. There are detailed directions WITH pictures to make the barefoot sandals.

Level: beginner - intermediate

You will need 7 or more different colored embroidery flosses.
You may choose to make them a solid color, in which case you’ll need 5.

Needle gauge is 2 for a tighter stitch, or 2.25.

The instructions are specifically for up to size 7, but there are instructions for how to add a row and make them bigger.