When you rip a CD to FLAC format the result is always lossless the only variable is in the level of compression. The level of compression does not affect the sound quality, only the amount of processing power and or time needed to compress and decompress the file as it plays.
Do you really mean an exact copy or an accurate rip.
An exact copy would be a bit by bit copy with no compression resulting in a file the same size as that on the original CD - so there would be no point converting this into another format.
An accurate rip is dependent on the quality of the drive being used and the condition of the CD. There is some software which will check the state of the file after ripping using (I believe) CRC checks -
http://www.dbpoweramp.com/ seems to be quite highly regarded although I have never used it myself.
I find MediaMonkey is the most straightforward piece of software for ripping and managing music.