If you want to add accessories to this to make it appear more authentic or because you're putting one together yourself, here's some extra ideas to help you.
Along with the Zori thong sandals which you've seen above, a Japanese woman or a man would also wear Tabi which are special socks. Tabi look something like regular ankle-high socks (often but not always in white) that have a separation between the big toe on each foot and the other toes. This is so they could be worn easily with thonged sandals.
You can take a normal pair of ankle-high socks, pull them so they are very loose over the toes before putting the thong sandals over the top - now there will be enough slack in the fabric to allow the shoes to be worn.
If you're making an outfit from a silky robe or dressing gown, you'll need a wide silky sash tied at the back to hold the robe neatly in place. You can purchase neck sashes which could also be used for this purpose - or simply sew some fabric into a long sash yourself.