I use clear as glass acrylic in the large pieces to avoid any smashing and cracking! and a toughened glass in the small 10cm x 10cm pieces. I use enamel paints and gild with gold, silver and copper leaf. The acrylic gives the exact same effect as glass and you can't tell the difference.
The acrylic is painted in reverse so the front of the piece is smooth and the artwork is on the back so you get a lovely depth to the artwork. Some of these pieces are in deep frames with a second piece of acrylic on the back which allows light through the design and lets the surroundings become part of the art.
The box frame pieces can be hung on the wall or free standing on a flat surface.