Place your cake mold on a clean surface. Arrange two strings cut from kitchen twines as in the photo below. The strings will be used to tie around the cake so make sure they are not too short.
Cut four pieces of banana leaves so that when you fold them in half and fold in half one more time, the folded piece fits inside the mold.
Put one folded piece of banana leaves inside the mold in an upright position against one corner of the mold as in the image below.
Pull the top corner down towards the bottom clockwise.
Lay flat and pull the farthest corner up to form a triangle at the bottom.
Continue to do the same for the other three pieces and put each of them in each corner. Note that for the last two pieces, you don't need to pull the corner to form a triangle.
Cut another four smaller pieces of banana leaves, about half as big as the previous ones and repeat those steps. This step will make sure the rice and mung bean are safely secured.
Once the leaves have been laid out, we can start adding ingredients. Scoop 1 cup of rice and pour into the mold, lightly spread and push the rice into an even layer.
Use your hands, break one of the mung bean ball in half, then hold one half above the rice and break into smaller pieces and spread over the rice.
Add half of the pork belly into the center over the mung bean.
Hold the other half of the mung bean ball above the pork belly, break into smaller pieces and spread over the cake center. Then finally top with about 1 1/4 - 1 1/2 cups of rice. Push some of the rice to the side and corners.
Fold the banana leaves down and press gently. Tie the two strings around the cake as below.
Remove the mold and tie two more strings around the cake. The rice will expand so don't tie too tightly. Now you can flip the cake over and it will look as in the photo.
Using the remaining ingredients to make another cake following the same steps.