Cut off both ends of the cucumber, rub to remove any bitterness, then rinse. Cut the cucumber in half lengthwise and slice into thin sticks. Rinse the pork belly, boil until cooked through, let cool, then slice thinly.

Crack the eggs into a bowl and beat well. Pour into a pan and cook into thin omelet layers (not too thick). Once cooked, remove and let cool slightly, then cut into strips about 1/2 inch (1 cm) wide.

Cut the Vietnamese pork sausage into thin sticks. Peel and finely chop the garlic. Finely chop the chili peppers. In a bowl, mix fish sauce, boiling water, and sugar, stirring until the sugar dissolves. Add lemon juice and stir well, then add the chopped garlic and chili, stirring gently so they float on top. Cut the rice vermicelli into shorter lengths, then arrange all the ingredients on a platter and enjoy assembling your own rolls.