To make a Turk’s head knot you need a cord of at least 100 cms
Fold by half and start with that loop formed at the fold, left end under the right end . Most of the cord should be on the right side rather than the left.
Now take the left side end and take it behind the first loop to the right and bring it over the right end of the cord
Now pick up the right end of the cord. You need to take it up and bring it to the left side weaving it through the loops ( over the first line, then under, then over and then under)
Now pick up the left end of the cord again, and carry it along the path followed by the cord earlier till the 4 loops are covered twice.
If you need a bigger knot you can continue the looping once more. Another option is to keep a small round button or marble or stone inside the knot before pulling it tight. This will give you a bigger knot.
Pull the knot till you get a tight ball or a loose knot, as per your preference. For making the button knot of the Chinese frog closures you need a tight knot.