Glass flooring, as glass stairs, is usually constructed of 2 or more glass panels, laminated together. 

General guidance for floors and stairtreads BS 6399: Part 1

Approximately 1m² is usually considered to be a practical maximum area for each panel - due to handling considerations.  The glasses should be installed with the thicker glass ply uppermost, and consideration must be given to the surface finish of the glass.

Glass dance floors for instance are usually specified in 15mm float laminated to 25mm float.  Corridors are 25mm laminated to 25mm, and for domestic dwellings, 10mm laminated to 19mm is more usual.