Use a hammer to break up two Terra cotta flower pots. To make it easier to contain the mess, place them in an old pillow case first.
Turn a 16-inch Terra cotta flower pot saucer upside down and place it on a piece of paper. Trace the circle. Turn the saucer right-side-up and trace the bottom of the saucer inside the larger circle. The inner circle will represent the bottom of the saucer, and the outer circle will represent the sides of the circle.
Place the broken up pieces of terra cotta from the first step into the two drawn circles from the second step. Arrange the pieces in a pattern you find appealing. Leave a 1/2-inch gap between each piece.
Prepare a cup of thin-set adhesive according to package direction. Apply the adhesive to the inside of the saucer using a paintbrush. Place the broken pieces of Terra cotta from the paper circle onto the adhesive. Work in two inch sections, applying more adhesive as you go.
Leave the saucer to sit for 48 hours to allow the thin-set to dry.
Prepare 2 cups of grout. Clean the surface of the mosaic using a damp rag. Apply the grout to the surface of the mosaic pieces using a trowel, making sure to press it between the pieces as you go. When you are finished, scrape the surface of the mosaic with a trowel to remove excess grout and smooth it.
Leave the grout to dry for 15 minutes. Wipe the surface of the grout with a damp rag. Then dry it with a dry cloth.
Place a tarp or plastic bag over top of the saucer and leave the grout to finish setting for 48 hours. To keep it from cracking, use a squirt bottle with water and mist the surface three times a day.
Seal the grout with a grout sealer applied with a paintbrush. Allow the sealant to dry.
Place your finished saucer on top of a birdbath base of your choice.