The photo above shows a two-tier crocheted flower with ties added to the center of the four squares. The flower is simply tied on by inserting a tie through a loop on each side of the joined squares center, then poking the ties back up through the center of the crocheted flower and tying in a loose double knot.
For the free pattern see: Two-Tier Flower With Ties. In the example shown in the photo above, I used two colors of worsted weight yarn and a U.S. size H hook to crochet the flower.
For the instructions for the afghan squares shown above, start on page 1 of this step-by-step.