Slumped tile designers start with flat glass, and melt it enough to curved the tile facing.
Shown here, small format slumped tiles - an alternative to flat edged, mosaic sized pieces.
Medium & large format slumped tiles
Slumped tiles used as a relief accent.
Surface variations can range from the dramatic to subtle.
Slumping used to create a relief image.
All slumped samples by Interstyle