Look for slightly tumbled glass cullet. This is the key to preventing cuts. The edges of tumbled glass aren't as sharp as freshly broken glass, but are still sharp enough to cut paper or string in a demonstration.
Spread out a 3-inch layer of the glass cullet in a tray with raised sides. Choose any size tray, but fill it with glass from edge to edge.
Move any pieces of glass that stick up sharply to the sides of the tray. This includes chunks of glass and the sides or corners of glass bottles.
Spread a piece of fabric over the cullet and pound the glass lightly with the bottom of a cast iron skillet. This helps to flatten the glass further, so no sharp or pointed edges are sticking up. Remove the fabric.
Step onto the glass barefoot. Slowly move one foot at a time as you walk on the glass. Press your foot against the cullet experimentally before applying your full weight to it. If you feel a pointed edge, seek out another spot to step on.
Brush off the soles of your feet with the soft brush before stepping from the glass cullet onto the floor. Brushing your feet helps remove any small splinters of glass you may have picked up.