Now you’re going to stack your flower piece on top of your backing piece, with both right sides facing up, NOT facing together. Line up the first st on each of these pieces. Remove your hook from the loop on the backing piece, insert it through the first st on the flower piece, grab that loop, and pull it through. 

Ch 1, SC through both pieces at the same time, all the way around, joining them together. Cut yarn, weave in ends.

Now for a little surface crochet, but only if you want!

Taking a new strand of the same color you used for your backing piece and holding it in back of your trivet, stick your hook through both trivet pieces together in the top of the VERY FIRST stitches you made, in the first round, and pull up a loop of yarn. Slip stitch around through the tops of all of your round 1 stitches, through both pieces, joining the centers together. When you get back around to your first stitch where you started, slip stitch into that one one more time, cut your yarn, and use a tapestry needle to pull the yarn through the first stitch to the back. Weave in ends.

And do it again if you want to, through the stitches in the second round! Do it all the same way, weave in your ends, and now the center of your trivet is connected together. This surface crochet used to join isn’t absolutely necessary, but it keeps the two pieces from flopping apart in the center.