Heat a tabletop grill (this is so the meat can be eaten hot off the grill). Spread the slices of pork belly (samgyeopsal) over the grill. You can also choose to slice the pork belly into smaller bits (the photo shows larger slices).
Also spread the mushrooms, onions and fresh peeled garlic cloves if you so desire.
Turn the slices over when one side is completely browned -- resist the temptation to constantly turn over. When both sides are browned, set them aside or better yet, deliver them directly to your eaters' plates. Don't be greedy -- be sure to take turns grilling so everyone has a chance to eat!
There are so many ways to eat samgeyopsal, like much Korean BBQ. Here are a just few: you can (1) dip slices of meat into the sesame oil sauce (기름장) - note this is best done while the meat is hot, (2) you can eat it sangchu ssam style (상추쌈) by wrapping up slices in lettuce leaves, with a daub of 쌈장 ssamjang (spicy paste) and a bit of rice, kimchi or whatever else you so choose, (3) instead of wrapping with sangchu, you can wrap with perilla leaves, (4) instead of wrapping with sangchu or perilla leaves - I know, this is getting confusing - you can eat it LA-style -- with a thin rice paper wrapping ... so good, or (5) you can eat a slice paired simply with a chopstick-ful of marinated green onions.