You will need:
a pair of geta with the toe loop already installed
and a shoelace
The shoelace can be decorative or plain.
If you need help making a pair of wooden sandals, there is an instructable for that:
Step 1: Loop the Toe Loop
Fold the top of the loop down to make two loops on the end.
Fold the two loops together.
Step 2: Add the Shoelace
Feed the shoelace through the holes in the rear of the geta and pull them tight.
Step 3: Cross the Shoelace
Step 4: Adjust the Strap
Insert your foot and pull on the shoelaces to adjust them to the size of your foot.
Step 5: Finalize the Strap
Loosen the toe loop
Feed the shoelaces through the toe loop
Make sure the shoelaces are adjusted the same as the old adjustment
Tighten the toe loop
Tie a knot in the shoelaces over the toe loop
Step 6: Tie Your Sandals
Step 7: Check the Fit and Enjoy
Readjust if necessary
Enjoy your footwear