A sheet of Lexan (polycarbonate) the appropriate thickness for your machine (mine was 1/8")
Fasten to the build plate at the edges with clips or tape.
Improve the adhesion by applying a coating of Glue Stick (normally used for gluing paper).
Model sticks to the build plate incredibly well.
When finished printing remove the Lexan from the machine with model attached.
Flex the Lexan to "pop" the model from the surface.
Clean the Lexan with water.
Repeat