Here is how I made them - first using 2 layers of fabric in a small embroidery hoop (a cotton topped with organza) I sewed on the beads (I threaded all 3 on the thread then put a stitch between each bead to hold in place) then using metallic thread did the ant's legs. For the leaf brooch I attached a leaf shape under the organza with iron on adhesive then outlined the leaf in split stitch.
Then I sewed all the layers around the edge together with backstitch before taking off the hoop and zigzagging around the edge with the machine.
Next I attached a couple of layers of padding to a large button, then ran a running stitch around the fabric. Once this is pulled tight around the button I stitch back and forward across the back to pull the fabric taunt around the button.
Next step is to cut a ciruclar piece of felt to cover the back. I choose to cut little slits and push the clasp ends through this as it makes a neater finish rather than stitch the clasp directly to the felt. Lastly sew with small stitches in thread matching the felt around the edge and voila - a finshed brooch. Depending on how much work you do in the embroidery on the front it is an easy evening of sewing.