Hello Der Alter,
The boards were actually wooden "trays" that held wax, but they were used primarily on a temporary basis... recording tax receipts or store receipts for the month, and then being transferred to a more permanent form of written record. The wax forms were also used for temporary court recording until they could be record and for land transfers, etc.
But, as we all know, the heat in Israel would melt the wax, therefore, it could only be a temporary form of written record.. and certainly, it would never be in a bound form as a permanent type of record.
~serapha~