Pour 1/8 cup of each liquid compound from the resin casting kit into a plastic cup. Stir it briskly for one full minute. The resin casting sets are easy to find in craft and art-supply stores, and they generally come in kits of two bottles for mixing at the time of casting.
Pour the gooey clear liquid into the mold you have selected. This can be a square, circle or any shape of mold that suits your tastes.
Snip the stem and excess foliage from the dried sunflower. Leave only the blossom and one or two leaves.
Press the dried sunflower face-down into the setting resin. Let the flower sink into the resin without pushing it in so deep that the substance gets on your fingers. Do not touch the resin. Set the mold in a dry place out of reach of disturbances for 20 minutes.
Pop the encased, perfectly preserved sunflower from the mold.