For art last week, we made coasters to give as Christmas gifts. (Isn't it funny how I say "For art last week", as though we do art every week?)
At Hobby Lobby, I purchased some coaster molds, stepping stone cement and mosaic glass.
We put a thin layer of Vaseline on the inside of each mold, then put cement to the top edge of the mold. We let the cement sit for five minutes before placing the glass pieces.
The coasters dried in the molds for 24 hours before we removed them. After removing, I placed them on a cookie cooling rack to let the underside cure for several hours. Then, I put some felt on the bottoms.