In a small bowl, combine water, dashi powder, soy sauce, and sake. Mix until combine.
Cut a small head of napa cabbage in half lengthwise and make sure to keep the core together and intact.
Wash the cabbage leaves gently without separating them from the core
Dry the cabbage with paper towel and layer 1-2 pieces of pork belly in between each napa cabbage leaf.
Once both halves are layered with pork belly slices, hold the cabbage together and cut off the core. Cut napa cabbage into 2-3 sections. Hold it tight and make sure to keep it together so they don't fall apart.
Arrange each section in a circular shape inside the pot and pack it tightly. Ensure the middle is also packed with more napa cabbage or you can also use seafood mushrooms (or other veggies) as well.
Pour your dashi mixture into the pot and put the pot on a stove. If you want it to be a traditional 'hot pot', place it on a portable stove!
On medium heat, cover with lid and let the dashi boil and cook the pork belly slices and napa cabbage.
When its fully cooked, you can eat each of the layers as is or dip it in ponzu sauce!
When you're halfway done, you can also add udon or other noodles to the dashi broth to make the meal more satisfying.