Whisk together the agave nectar, soy sauce, fermented fish sauce and lime juice.
Cross hatch slice through the skin of the pork belly about 1" apart.
Place the pork belly in a stainless steel or non-corrosive bowl and cover with the marinade for 24-48 hours turning frequently.
Place the pork belly in a half 200 pan with 2 cups the marinade and enough water to come half way up the pork belly. Cover and cook at 275 degrees for 3-4 hours until the pork belly is tender and a skewer can penetrate with very little resisitence.
Remove the pork from the liquid, cool and cut into 1" cubes.
Lightly dust the pork cubes with flour and deep fry a few minutes until they are carmelized and crunchy. Do not burn!
Place on paper towels and sprinkle with salt if needed.
For the Pickled Watermelon
Cut watermelon into 1" cubes - remove seeds and refrigerate. Reserve the rind.
Carefully remove the green skin from the rind and cut the rind into 1/2" cubes.
Bring all ingredients for the pickling liquid to a simmer and strain over the watermelon rinds.
Refrigerate the marinade for at least 1 hour to up to 2 days.
For the Dressing
In a blender, puree the brown sugar, ginger, cilantro and garlic with the canola oil.
In a slow, steady stream with motor running add the vinegar and lime juice