In a bowl, mix together gochujang, soy sauce, rice vinegar, garlic, ginger, sesame oil, sugar, sesame seeds and white part of green onions.

Put the pork belly in a freezer bag with the gochujang sauce, and remove the air through a vacuum sealer or the displacement method. Put the bag in the fridge, and let the pork marinade for 4 to 24 hours (optional, but recommended).

Set sous vide machine to 74C/165F. Once the target temperature is reached, drop pork belly in the bath for 10 hours.

Remove bag from bath, and immediately transfer bag to an ice bath to cool down the pork belly. Once cooled, take pork belly out, pat dry and slice the belly into ¼-inch lengthwise pieces.

Heat small sauce pan on medium, add gochujang sauce from bag and simmer for 3 to 5 minutes. Once thickened, turn off heat and add pork belly to evenly coat each slice. Leave extra sauce for a second coat. Remove slices from pan and arrange them on a foil-lined baking sheet.

Set oven to 350F. Place baking sheet in oven for 5 to 7 minutes. Remove from oven, and re-coat the pieces with remaining sauce. Switch to broil mode and finish for another 1 to 2 minutes. Remove from oven, and cut in to desired piece size. Garnish with green onions and sesame seeds, and serve with fried rice, noodles, and/or vegetables. Enjoy!