hours in advance, fill the sous vide to the fill line with water and set the temperature for 160 F.
Pat the pork belly dry and sprinkle liberally with salt. Slide it into a sous vide bag thats been sealed on one end and is about twice as long as the cut of meat. Set aside.
In a medium sauce pan, combine the preserves, coffee, honey, balsamic vinegar and Worcestershire sauce. Stirring frequently, bring to a boil over high heat. Reduce the heat to medium and, still stirring frequently, simmer until the mixture has reduced and is thick and syrupy. Allow the coffee/peach mixture to cool a bit, then season to taste with the red pepper flakes and salt.
Carefully pour the syrup into the bag with the pork belly and seal - the bag should be long enough and the syrup thick enough that it isnt sucked out when the bag is sealed (you can use the gentle setting if the vacuum sealer has one).
Place the sealed pork belly into the sous vide and cover. Cook for 24 hours.
Remove the sealed bag from the sous vide. Carefully cut open the bag and remove the pork belly, placing it fat-side up on the top of a vented broiler pan - do not pat or wipe off any of the liquid clinging to the meat. Discard the liquid in the bag.
Place the pork belly about 3 inches beneath the broiler of the oven and broil on high for 5 to 7 minutes, or until the top is crisp and browned. Remove from the oven and allow the pork belly to rest for about 5 minutes before slicing and serving.