You can use Boxoft All to Amr Converter to switch kinds of audio files (MP3, TTA, OGG, APE, WMA, WAV and FLAC) to small size ARM format. as you known, most mobile phone support AMR format because its volume is so small that you can make it into ringtone.
Click "Add" or "Add folders" to add FLAC files;
Click "Convert to AMR" button to start converting.