Google a program called DVDAudiofile. It’s free and it handles FLAC files natively. It is designed to make a DVD-Audio compliant disc which will not play in all DVD players. You need one that conforms to the DVD-A specification or you can play it in any number of software packages like Nero Showtime, WinDVD, or PowerDVD.
Alternatively, if you need compatibility with non-DVD-A compliant hardware, try Googling a program called WAVtoAC3 which, after decoding the FLAC files to WAV, should be able to encode them as AC3 streams for decoding by any settop DVD player.
PigPenz is right about the MASI discWelder products, the Steel and Chrome editions have an automirror feature which will encode any WAV files from the Audio zone into Dolby Digital AC3 streams and place them in the Video zone. These are pricey products aimed at professional studios.
Post back if you have questions about DVDAudiofile or WAVtoAC3 as I’ve used both of them.