Make decorative vases with air dry clay following this tutorial from "Craft & Creativity". These lovely vases with stamped designs start out as a slab of clay flattened with roller (or pasta machine). Cooking oil is used as a release agent when forming clay around glass.
I'd suggest Creative Paperclay for this project but many brands of ADC should be suitable, including the inexpensive Crayola Air Dry Clay or the heavy DAS terra cotta clay. The really soft clays probably won't retain a stamped impression very well.
Remember, all air dry clay will shrink some, so be sure to remove from glass armature to dry or you may find a lot of cracks in cured clay.
Keep in mind that, even when cured, air dry clay is water soluble...so you must use the test tubes to hold water as shown in tutorial or another type of glass insert. Of course, artificial flowers won't need any water! ;-) LOL
Inspiration and ideas for other styles: