Can I add flash memory to 27'' 2012 late imac?

Already I have 2012 late 27''imac with 1TB HDD. Is it possible to add a flash memory inside and install a fusion drive? If yes, then how the OSX will be installed - like the original for 1TB harddrive that I woud have to volumes - SSD and HDD or like for Fusion drive when OS X ceates a one volume and add apps that I use the most to flash but large files and unused programs to HDD? I would like to have the original OS X for Fusion drive so all woud run like it have to.

I found this Fusion drive installation : http://a.wholelottanothing.org/2013/03/how-to-make-your-own-fusion-drive.html