For anyone running OS X and finding this question from Google, I would suggest following the method listed here and using ffmpeg
in the Terminal.
Install homebrew:
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
Then install ffmpeg and all its libraries:
brew install ffmpeg
brew install ffmpeg --with-fdk-aac --with-ffplay --with-freetype --with-libass --with-libquvi --with-libvorbis --with-libvpx --with-opus --with-x265
Then within the terminal, navigate to the folder containing the FLAC files to be converted and run ffmpeg's converter with something like this:
for q in *.flac; do echo "$q"; ffmpeg -i "$q" -aq 0 "${q%%flac}mp3"; done
Credit goes to the original poster of the above command at the linked thread.