Line a 5- to 6-quart slow cooker with some of the banana leaves, shiny-side up. Add the pork, ginger, soy sauce, sugar and a big pinch of salt and toss well to coat (leaving the banana leaves in place). Fold any banana leaf overhang over the meat and top with another piece of banana leaf, tucking the leaves down the sides of the slow cooker so that the pork is completely enclosed.
Cook on the low setting until the meat is falling apart, 6 to 8 hours. Transfer to a bowl (discard the leaves) and garnish with the cilantro.