There seem to be many ways to spell this Islamic method of making tiles, but perhaps it is correctly spelt zillij.
Having researched it a bit more, I was fascinated to find out that once the biscuit fired tiles are cut into shapes , glazed and put together as whole geometric tiles, it doesn’t end there! They don’t just slap up the tiles on the facades of buildings. According to one firm in Fez they use the single cut and glazed pieces, known as furmah and lay them all glazed side down on the floor in a pattern, like a symbolic geometric puzzle (each shape has a meaning ). Then they pour 3 inches of concrete over the back, wait until it dries and install the whole piece in one panel. The following article in the link describes this practice. The mosaic they install is 1 square metre, which is surprising as it must be very heavy.