Here's how to do it.
2. Work 6 single crochet in the second chain from the hook.
3. Without joining or turning, work 2 single crochets in each single crochet around, for a total of 12 single crochets.
4. For the next round, work 1 single crochet in each single crochet around (for a total of 12 single crochets). Then close the button by decreasing 1 single crochet in each 2 single crochets, for a total of 6 single crochets in the last round.
5. Using the 12-inch tail that was left at the beginning, weave the tail in and out of the last 6 stitches and pull tight to complete the button.
Now work whatever fanciness you have planned for the necklace, and when the necklace is done, you'll work the button loop on the opposite side.
6. To work the button loop, work 12 chain stitches at the end of the necklace.
7. Join with a slip stitch in the 12 chain from the hook to form the button loop.
8. Work 12 single crochets in the button loop to make it nice and firm.
9. Now finish off your thread and weave in all the ends. You should have a button loop perfectly sized to fit over the button made at the beginning.